Electric   toy  mak- 


Southern  Branch 
of  the 

University  of  California 


Los  Angeles 


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ELECTRIC  TQY  MAKING  FOR 
AMATEURS 


IXCLri)/N(,'  BATTERIES,  MAGNETS,   MOTORS, 

MISCELLANEOUS    TOYS   AND   DYNAMO 

CONS  TR  UCTION 


BY 
T.  O' CO  NOR  SLOANE    E.M.,  A.M.,  PH.D. 

UTHOR     OF 

"  Electricity  Simplified,"  "  Arithmetic  of  Electricity,''  etc.,  etc. 


Jlllnstrateb 


NEW  YORK 

MUNN   &   CO. 
1899 


COPYRIGHT,  1891,  BY 
NORMAN  W.  HENLEY  &  CO. 


TK 
991  \ 

S&3 


PREFACE. 


ELECTRIC  TOY  MAKING  is  a  very  comprehensive 
title,  one  which  may  be  made  to  embrace  far  more 
ground  than  this  work  pretends  to  cover.  In  the 
realms  of  amateur  work  of  all  kinds — mechanics,  nat- 
ural science,  and  even  legerdemain  or  natural  magic — 
electricity  can  be  made  to  play  an  important  part. 
The  methods  of  applying  it  to  simple  constructions, 
within  the  reach  and  scope  of  amateurs,  constitute 
the  theme  of  this  book.  The  effort  has  been  to  pre- 
sent the  reader  with  a  suggestive  line  of  experimenta- 
tion and  construction,  and  to  open  a  field  within 
which  his  own  ideas  can  have  indefinite  scope  and 
extent.  It  is  believed  that  little  in  the  way  of 
actual  toy  making  can  be  done  outside  of  the  general 
limits  here  defined.  Thus,  as  adjuncts  to  a  static 
electric  machine,  Holtz  or  Winshurst,  a  quantity  of 


vi  PREFACE. 

pieces  of  apparatus  might  have  been  described,  but 
such  appliances  do  not  deserve  to  be  called  toys  in 
any  sense. 

It  is  hoped  that  the  work  will  prove  fertile  in  the 
suggestive  sense.  Many  things  are  presented  which 
are  susceptible  of  almost  any  quantity  of  modifica- 
tions. The  motors  have  been  selected  with  regard  to 
their  variation  from  the  usual  type  of  "  reversible 
dynamo."  The  simple  experiments  and  construc- 
tions given  under  static  electricity  are  made,  as  far 
as  possible,  independent  in  action,  except  as  far  as  an 
induction  or  spark  coil  and  battery  may  be  needed  to 
operate  some  of  them. 

As  a  good  workman  is  known  by  his  tools,  so  is  the 
electrician  judged  by  his  battery.  The  few  hints 
given  as  to  the  use  of  batteries  should  tend  to  put 
the  amateur  on  a  proper  footing  at  the  all-important 
foundation  and  basis  of  his  operations.  "With  a  well- 
kept  battery  the  neatly  constructed  apparatus  will 
appear  to  double  advantage,  and  its  effectiveness  will 
be  secured.  Apparatus  is  often  blamed  for  the  short- 
comings of  the  current-generator. 


CONTENTS. 


CHAPTER  I. 
BATTERIES. 

Primary  Batteries  in  General — Batteries  with  Electric 
Light  Carbons— A  Tomato  Can  Battery— Materials  for 
Battery  Cells 9 

CHAPTER  II. 
PERMANENT  MAGNETS. 

How  to  Magnetize  Steel  Bars — Rolling  Armatures — 
Mahomet's  Coffin — Magnetic  Jack-straws — The  Magnetic 
Top— The  Magnetic  Pendulum— Mayer's  Floating  Needles 
— Magnetic  Fishes,  and  the  Magnetic  Swan,  Boat,  etc.  ...  23 

CHAPTER  III. 
ELECTRO-MAGNETS. 

Construction  of  Electro-Magnets — Magnetizing  Coils — 
The  Magic  Circle— Magnetic  Hemispheres 37 

CHAPTER  IV. 
ELECTRIC  MOTORS. 

Pendulum  Coil  Motor — Recordon  Magnet  Motor — Multi- 
polar  Motor — Page's  Rotating  Armature — The  Electric 
Locomotive .  46 


viii  CONTENTS. 

CHAPTER  V. 
ELECTRIC  BELLS. 

The  Tolling  Bell— The  Vibrating  Bell— The  Safe  Pro- 
tector       65 

CHAPTER  VI. 
MISCELLANEOUS  TOYS. 

The  Electric  Dancer— The   Magic  Drum— The   Electric 
Hammer — Electric  Insects — The  Incandescent  Lamp 73 

CHAPTER  VII. 

SPARK  AND  INDUCTION  COILS,  AND  ALLIED  SUBJECTS. 
The  Spark  Coil — The  Induction  Coil — Recordon's  Induc- 
tion Coil— The  Magneto-Generator—Electric   Artillery- 
Electric  Gymnastics — Ano-Kato — Simple  Experiments  in 
Static  Electricity  89 

CHAPTER  VIII. 

HAND  POWER  DYNAMO. 

Page 121 

CHAPTER  IX. 

MISCELLANEOUS  RECEIPTS  AND  FOHMUL.E. 
Page 12U 


CHAPTEE  I. 

BATTERIES. 

PRIMARY  BATTERIES  IN  GENERAL — BATTERIES  WITH 
ELECTRIC  LIGHT  CARBONS — A  TOMATO  CAN  BAT- 
TERY— MATERIALS  FOR  BATTERY  CELLS. 
Primary  Batteries  in  General. 

THE  requirements  of  a  good  battery  are  easier  stated 
than  secured.  It  should  be  constant,  of  low  resist- 
ance, and  of  good  electro-motive  force.  The  latter 
factor  should  not  fall  below  one  volt.  For  this  reason 
the  caustic  soda  batteries  are  hardly  to  be  recom- 
mended unless  the  amateur  is  willing  to  use  a  large 
number  of  cells. 

For  constancy  and  cheapness  the  sulphate  of  copper 
cells  lead.  The  quality  of  cheapness  appertains  both 
to  original  cost  and  expense  of  running.  A  great  ob- 
jection is  their  high  resistance;  for  this  reason  a  very 
large  battery  may  seem  to  have  but  little  power.  If 
an  effort  is  made  to  reduce  their  resistance,  by  bring- 
ing the  plates  closer,  copper  is  deposited  on  the  zinc. 

Tl\e  depositi'  n  of  copper  on  the.  positive  plates  is 
not  only  annoying,  as  exacting  scraping  and  cleaning, 
but  exhausts  the  solutions.  It  does  not  do  to  bring 
the  plates  too  close  together. 


10  ELECTRIC  TOY  MAKING. 

This  is  one  reason  for  high  resistance,  but  there  is 
a  greater  one.  It  is  that  the  solutions  either  of  zinc 
or  copper  sulphate  in  the  cell  are  never  of  low  resist- 
ance. Such  solutions  do  not  compare  with  dilute 
sulphuric  acid  for  conductivity. 

Owing  to  its  constancy  and  cheapness,  the  sulphate 
of  copper  combinations  form  favorite  batteries  with 
telegraph  operators.  In  the  Daniell  battery  a  plate 
of  zinc  is  contained  in  a  porous  cup  surrounded  by  a 
plate  of  copper  The  three  are  placed  in  a  ghiss 
jar  A  solution  of  zinc  sulphate  is  poured  into  the  por- 
ous cup;  a  solution  of  copper  sulphate  into  the  outer 
jar.  In  the  gravity  battery  only  the  glass  jar  and  two 
plates  are  used.  The  copper  plate  is  in  the  bottom 
and  a  gutti-percha  covered  wire  leads  from  it.  The 
zinc  plates  are  near  the  top  of  the  jar.  To  charge  it, 
water  is  introduced  until  the  zinc  is  covered.  A 
handful  of  crystals  of  copper  sulphate  are  added  with 
a  little  zinc  sulphate  solution  if  necessary.  Gravity  is 
here  relied  on  to  keep  the  two  solutions  separate;  the 
zinc  sulphate  increases  in  quantity  with  the  working 
of  the  battery,  but  the  copper  sulphate  solution  is 
kept  }'.s  strong  as  possible.  After  a  while  the  zinc 
sulphate  solution  will  exceed  in  specific  gravity  the 
copper  sulphate  solution,  when  the  battery  will  cease 
to  act  properly.  Hence,  the  upper  layers  of  liquid  are 
withdrawn  from  time  to  time  and  replaced  by  plain 
water. 

The  Leclanche  battery,  befure  the  introduction  of 


BICHROMA TE  BATTERIES.  1 1 

the  dry  batteries,  was  the  great  open  circuit  battery. 

For  intermittent  work  either  typo  can  now  be 
recommended.  For  constant  and  heavy  work  neither 
is  of  any  utility  whatever. 

For  heavy  work  the  bichromate  cells  are  the  best, 
all  things  considered.  They  are  not  very  constant 
and  with  a  heavy  output  soon  begin  to  run  down. 

Of  them  the  Bnnsen  battery  is  to  be  recommended 
for  constant  currents  of  long  duration.  The  cell  con- 
sists, in  brief,  of  a  porous  cup  and  outer  jar.  in  on 
of  the  divisions  an  amalgamated  zinc  plate  is  con- 
tained ;  in  the  other  division  a  carbon  plate.  The  car- 
bon is  surrounded  by  a  strong  solution  of  chromic  and 
sulphuric  acids.  The  latter  imparts  conductivity;  the 
former  is  the  depolarizer.  The  zinc  is  surrounded 
with  dilute  sulphuric  acid.  The  two  solutions  inevi- 
tably diffuse  one  into  the  other.  The  more  they  are 
kept  distinct  the  better  the  condition  of  the  battery  is. 

The  plain  bichromate  battery  consists  of  a  jar  con- 
taining the  amalgamated  zinc  and  carbon  plates  and 
charged  with  the  chromic-sulphuric  acid  solution. 
This  is  a  defective  combination.  The  chromic  acid 
acts  upon  the  zinc,  and  the  battery  rapidly  deteriorates 
when  on  open  circuit. 

The  latter  trouble  is  avoided  by  removing  the  plates, 
or,  at  any  rate,  the  zinc  plate,  when  the  cell  is_notin 
use.  This  practise  economizes  solution  and  is  by  all 
means  to  be  recommended.  Various  mechanical  con- 


13  ELECTRIC  TOT  MAKING. 

structions  have  been  adopted  for  raising  the  plates. 
Such  batteries  are  termed  dip  batteries. 

The  solution  to  be  used  should  be  carefully 
prepared.  An  inferior  mixture  gives  very  inferior 
results.  The  following  is  the  celebrated  Trouve 
solution  and  can  be  highly  recommended: 

It  requires — 

Water 8        pints. 

Powdered  Potassium  Bichromate 1 2-10  Ibs. 

Concentrated  Sulphuric  Acid 3610  Ibs. 

The  bichromate  is  added  to  the  water  and  stirred 
well  through  it.  The  acid  is  slowly  added,  with 
constant  stirring.  A  glass  rod,  and  glass,  or  well 
enamelled  iron  vessels  should  le  used  for  the  mixing. 
As  the  acid  is  added  the  temperature  rises  and  all, 
or  nearly  all,  of  the  bichromate  dissolves.  Some- 
times to  four  parts  of  water  as  much  as  one  part  of 
bichromate  is  added,  with  nearly  two  p:irts  of  sul- 
phuric acid.  All  parts  are  by  weight.  The  secret  is 
in  the  fine  pulverization  of  the  bichromate  and  in 
the  gradual  addition  with  constant  stirring  of  the 
acid. 

Great  care  should  be  taken  in  pulverizing  the  bi- 
chromate to  inhale  none  of  the  dust,  as  it  may 
cause  ulcers. 

The  above  solution  may  be  employed  in  the  car- 
bon plate  division  of  the  Bunsen  cell  with  excellent 
results. 


SAL  AMMONIAC  BATTERIES.  13 

For"  the  zinc  plate  division  of  the  Bunseii  cell,  one 
part,  by  weight,  of  sulphuric  acid  to  twelve  of  water 
is  used. 

Very  useful  little  batteries  may  be  constructed  by 
using  a  mixture  of  two  parts  sal  ammoniac  with  one 
part  of  mercurous  or  white  mercury  sulphate  in 
water  as  the  excitant.  Zinc  and  carbon  are  the  ele- 
ments and  are  contained  in  a  single  cell. 

A  piece  of  old  battery  carbon  may  be  bored  out  for 
part  of  its  length  and  used  as  both  the  cup  and  neg- 
ative element  at  once.  It  should  be  well  paraffined  by 
dipping  in  melted  paraffine  wax.  A  zinc  rod  or  wire 
small  enough  to  enter  the  hole  having  some  rubber 
bands  wound  around  it,  is  inserted  as  the  positive 
plate.  The  bands  must  cover  as  little  of  its  surface  as 
possible  and  its  bottom  must  not  touch  the  carbon. 
The  sal  ammoniac-mercurous  sulphate  solution  is  the 
excitant.  A  little  of  the  mixture  is  placed  in  the  cup, 
some  water  is  added  and  mixed  with  it.  The  zinc  is 
placed  in  position,  and  all  is  ready  for  use. 

Such  a  battery  is,  of  course,  more  of  a  curiosity 
than  a  practical  source  of  current. 

For  working  small  apparatus  the  silver  chloride 
cell  has  been  very  highly  thought  of.  Although  orig- 
inally of  somewhat  high  cost  the  silver  is  not  lost  and 
can  readily  be  reconverted  into  chloride  when  the 
battery  becomes  exhausted. 

A  test  tube  made  of  extra  thick  glass  will  answer 
for  the  cell.  A  piece  of  sheet  zinc  is  bent  so  as  to  fit 


14  ELECTRIC  TOT  MAKING. 

closely  in  the  tube,  in  contact  with  its  sides.  A  lug 
or  projecting  piece  extends  up  from  the  zinc.  The 
plate  should  he  nearly  as  1<  ng  as  the  tube.  It  must 
be  well  amalgamated  and  put  in  position. 

Next,  a  very  thin  pi<cc  of  silver  foil  is  wrapped 
around  a  rod  of  wood  the  size  of  a  lead  pencil.  A 
silver  wire  is  soldered  or  otherwise  connected  to  this 
to  act  as  terminal.  A  thick  paste  of  silver  chloride 
and  water  is  spread  upon  a  piece  <  f  blotting  paper, 
which  is  just  long  enough  to  go  once  around  the 
silver.  This  is  then  wrapped  around  the  foil  with  the 
chloride  paste  against  the  silver. 

A  strip  of  muslin  is  Avrapped  two  or  three  times 
around  the  blotting  paperand  is  neaily  sewed  ortied. 

A  thick  rubber  band,  best  a  section  from  some 
rather  heavy  gas  tubing,  is  put  over  each  end  of  the 
silver  element.  It  must  fit  without  squeezing.  A 
perforated  slice  of  cork  will  answer  us  well.  The 
silver  element  is  dropped  into  place,  and  the  tnbe  is 
filled  with  a  solution  of  sal  ammoniac  in  water. 

Such  a  cell  is  without  local  action,  and  represents 
a  very  small  open  circuit  battery.  Two  or  three  will 
operate  a  small  induction  coil.  Their  durability  de- 
pends on  the  amount  of  silver  chloride. 

As  no  gas  is  generated,  the  cells  may  be  enclosed 
hermetically  by  corks,  coated  or  covered  with  a  thick 
layer  of  sealing-wax  or  cap-cement.  They  form  a 
convenient  pocket  battery.  Sometimes  they  are 


ELECTRIC  LIOHT  CARBONS.  15 

made  in  soft  rubber  tubing,  closed  at  both  ends  with 
corks  and  cement  as  above. 

The  present  work  docs  not  purport  to  treat  of  bat- 
teries, yet  it  has  seemed  well  to  say  this  much  on  the 
subject  and  to  give  some  examples  of  the  utilization 
of  common  material  for  the  purpose  in  the  next 
sections. 

For  temporary  purposes  a  battery  of  great  power  is 
easily  made  up  by  using  the  bichromate  solution,  with 
zinc  and  carbon  as  the  elements,  and  any  convenient 
porcelain  or  glass  vessels  as  the  cups  or  jars.  For 
permanent  batteries  considerable  may  be  done  in  the 
way  of  neat  mounting,  etc.,  to  make  them  attractive 
objects  to  the  eye  of  the  amateur  electrician. 

One  concluding  word  must  be  said  :  Never  attempt 
to  use  unamalgamated  zincs  in  a  bichromate  cell.  To 
amalgamate,  place  a  little  globule  of  mercury  in  a 
saucer  with  some  dilute  sulphuric  acid.  Wet  the 
zinc  plate  with  the  acid.  Then,  with  a  bit  of  zinc  or 
galvanized  iron,  rub  the  mercury  well  over  the  sur- 
face of  the  zinc  plate. 

In  the  cut  of  the  electric  light   carbon   battery, 
page    18,   the   arrangements  for   amalgamating   are 
shown.     The  slip  of  galvanized  iron  in  the  saucer   is 
bent  so  as  to  fit  around  the  circular  zinc  rods. 
Batteries  with  Electric  Light  Carbons. 

Electric  light  carbons  make  excellent  material  for 
the  negative  plate  of  batteries.  They  may  be  used 
in  various  ways  as  regards  their  mounting. 


16  ELECTRIC  TOY  MAKING. 

The  first  thing  to  be  done  to  them  is  to  remove  the 
copper  plating  from  such  portions  as  are  to  be  im- 
mersed in  the  acid  or  battery  fluid.  This  is  easily 
effected  by  immersion  in  dilute  nitric  acid  to  the 
desired  depth.  A  few  seconds  will  generally  suffice 
to  strip  the  metal.  * 

The  next  step  depends  on  how  they  are  to  be  used. 
Old  rejected  pieces,  such  as  the  lamp  trimmers  throw 
away,  may  be  employed  in  some  constructions.  If  the 
pieces  are  short,  an  excellent  system  is  the  following: 

For  each  battery  jar  one  long  piece  is  selected.  The 
copper  is  removed  from  its  lower  part,  one  or  two 
inches  at  one  end  being  left  plated.  It  is  then  washed 
and  dried  in  an  oven.  To  the  upper  or  coppered  end 
while  still  hot,  or  if  it  has  cooled,  while  heated  gently, 
paraffine  wax  is  applied  just  below  the  copper,  until 
the  porous  carbon  has  absorbed  all  that  it  can. 

The  smaller  pieces  of  carbon  are  completely 
stripped  of  copper.  The  long  piece  is  placed  upright 
in  a  porous  cup  and  the  small  pieces  are  packed 
in  around  it.  This  makes  the  negative  element. 
The  wire  is  wound  around  the  coppered  end  and 
may,  if  desired,  be  soldered  thereto.  It  is  also 
possible  to  drill  a  small  hole  in  the  top  and  screw 
in  a  binding  post,  which  may  be  further  secured  by 
soldering. 

The  illustration  presents  another  method.  To  carry 
it  out  the  carbons  must  be  rather  long,  according  to 
the  average  of  the  rejected  pieces.  The  copper  is  dis- 


NEOA  TIVE  PL  A  TES.  1 7 

solved  from  their  lower  portions,  leaving  one  or  two 
inches  coppered.  They  are  washed,  dried  and  paraf- 
fined as  just  described. 


FIG.  1.— MAKING  NEGATIVE  PL&TES  FROM  ARC  LIGHT  CARBONS. 


They  are  next  placed  on  a  board  and  secured  as 
shown  by  a  strip,  X.  As  carbons  are  often  slightly 
bent,  care  should  be  taken  to  turn  them  until  they  lie 
as  fully  in  contact  as  possible.  A  couple  of  side 
blocks,  abutting  against  a  straight  end  piece,  form  a 
pocket  to  receive  the  coppered  ends,  which  are 
pressed  together  by  the  wedge,  TV. 

With  soldering  acid,  solder  and  soldering  iron,  the 
ends  are  now  soldered  together.  The  solder  is 
melted  into  the  grooves  formed  by  the  contiguous 
carbons.  After  cooling,  the  carbons,  now  united,  are 
turned  over,  are  again  secured  as  shown  and  the 
opposite  sides  are  soldered. 

This  gives  what  is  practically  a  solid  battery  plate, 
and  which  really  possesses  special  advantages  in  its 


18  ELECTRIC  TOT  MAKING. 

increased  area  of  surface.     A  binding  post   can   be 
soldered  into  one  of  the  grooves. 

Another  way  of  uniting  carbons  is  to  cast  lead 
around  the  ends  of  a  bunch,  instead  of  soldering. 
This,  however,  makes  a  heavy  plate  only  adapted  for 
large  batteries. 


FIG.  2.— ELECTRIC  LIGHT  CARBON  BATTERY. 

An  excellent  method  is  illustrated  in  the  next 
cut.  It  is  to  cut  out  a  circular  or  square  piece  of 
wood  to  cover  or  else  to  simply  extend  across  the 


ELECTRIC  LIGHT  CARBON  BATTERIES.        19 

top  of  the  jar.  Holes  are  bored  in  it  through  which 
the  carbons  are  tightly  thrust  after  stripping  and 
paraffining.  The  ends  are  brought  just  flush  with  the 
surface  of  the  wood,  and  a  strip  of  brass  or  copper  is 
sweated  to  the  plated  carbon  ends.  This  is  done  by 
first  tinning  the  lower  surface  of  the  brass  plates, 
where  it  is  to  come  in  contact  with  the  carbons,  and 
then  tinning  each  carbon  top.  The  strip  is  now  laid 
in  position,  and  by  heating  it  the  two  sets  of  tinned 
surfaces  are  caused  to  unite  by  the  solder  running 
together.  The  brass  plate  is  pressed  down  and  held 
so  until  the  solder  is  partly  cooled  and  has  set  or 
ha  dened. 

If  the  ends  are  not  plated  a  piece  of  copper  foil  can 
be  forced  into  the  hole  with  the  carbon,  and  to  this  a 
wire  is  soldered  connecting  all  the  carbons  together. 
The  foil  can  be  doubled  over  the  top  of  the  carbons, 
and  the  connecting  strip  of  foil  used  as  just  described. 

As  regards  zincs,  old  Lcclanche  battery  zincs  can  be 
used  in  a  similar  way  by  thrusting  them  through 
holes  in  a  board.  All  the  soldering  must  be  done 
before  the  zincs  are  amalgamated. 

A  very  neat  battery  is  made  by  cutting  out  the 
wood  to  cover  the  jar,  and  giving  it  a  rebate  all 
around  its  edge,  so  that  it  cannot  slip.  The  zincs 
and  carbons  are  then  fastened  in  holes  as  just 
described.  For  a  single  fluid  battery  this  is  an 
excellent  form  of  construction. 

The   wooden  top  may   be  made  of  pine,    or,    if   a 


20  ELECTRIC  TO  7  MA  KING. 

hard  wood  is  desired,  mahogany  or  maple  is  good. 
Ash  is  not  altogether  satisfactory,  because  if  the 
lower  surface  gets  wet  Ihe  piece  warps  badly.  But 
this  is  of  less  importance,  as  the  greatest  care  should 
be  taken  to  avoid  such  wetting  as  the  acid  will  cor- 
rode the  connections. 

It  will  be  seen  also  that  a  binding  post  can  in  this 
battery  be  screwed  through  a  hole  in  the  brass  or 
copper  strips  directly  into  the  wood,  and  then,  if 
desired,  may  be  soldered. 

A   Tomato  Can  Battery. 

The  above  designation  applies  to  a  simple  form  of 
home-made  battery  in  which  a  discarded  tomato  can 
may  be  made  to  play  a  part.  It  is  a  battery  of  con- 
siderable merit,  but  of  too  low  voltage. 

The  outer  vessel  for  containing  the  fluids  and  other 
parts  of  the  battery  is  a  tomato  can  or  other  iron  ves- 
sel. Within  it  is  a  porous  cap.  The  annular  space 
between  is  filled  with  fine  scrap  iron,  such  as  turnings, 
borings  and  clippings.  A  zinc  plate  goes  into  the 
porous  cup. 

The  exciting  solution  is  a  ten  per  cent,  solution  of 
caustic  soda.  The  wires  are  connected  as  shown,  one 
to  the  zinc  plate  and  one  to  the  can  itself. 

The  battery  is  liable  to  polarization,  but  the  large 
surface  of  the  iron  protects  it  to  some  extent. 

If  it  is  desired  to  make  it  constant  or  self-depolariz- 
ing, a  quantity  of  oxide  of  copper  may  be  placed  in  the 


TOMATO  CAN  BATTERIES.  21 

bottom  of  the  jar  upon  a  layer  of  iron  borings  and  the 
rest   of  the  filling  of  iron  scraps  may  be  dispensed 


FIG.  3.    A  TOMATO  CAN  BATTKBT. 

with.     This  makes  it  a  Lalande-Chaperon    battery. 
The  E.  M.  F.  is  about  .75  volt. 

Materials  for  Battery  Cells. 

Before  leaving  the  subject  a  word  may  be  said  on 
the  cell  proper.  Porcelain  marmalade  jars  make 
excellent  receptacles  for  small  couples.  In  selecting 
a  vessel  there  is  one  point  of  special  importance.  The 


22  ELECTRIC  TOT  MAKING. 

sides  should  not  taper  or  slope  outwards.  It  is  far 
letter  to  have  a  vessel  that  is  smaller  at  the  neck  than 
at  the  bottom.  Self-sealing  preserve  jars  for  this 
reason  are  very  serviceable. 

Wooden  battery  troughs  have  been  used  to  a  con- 
siderable extent.  These  may  be  made  of  pine,  oak, 
mahogany  or  maple.  The  sides  maybe  protected  from 
the  liquids  by  baking  and,  while  hot,  coating  with 
melted  paraffine.  Potassium  bichromate  battery  so- 
lution, however,  will  in  time  attack  almost  anything 
except  glass  or  porcelain. 

A  long  trough  to  contain  a  number  of  elements 
may  have  its  partitions  made  of  glass  set  in  grooves  in 
the  sides  and  secured  with  cement. 


CHAPTER  II. 
PERMANENT  MAGNETS. 

HOW  TO  MAGNETIZE  STEEL  BARS — ROLLING  ARMA- 
TURES— MAHOMET'S  COFFIN — MAGNETIC  JACK- 
STRAWS — THE  MAGNETIC  TOP — THE  MAGNETIC 

PENDULUM — MAYER'S     FLOATING      NEEDLES — 
MAGNETIC  FISHES,  AND  THE  MAGNETIC  SWAN, 

BOAT,    ETC. 

How  to  Magnetize  Steel  Bars. 

A  BAR  of  soft  iron  held  iu  a  magnetic  field,  is 
acted  on  by  the  lines  of  force  constituting  the  field, 
and  becomes  a  magnet  and  will  attract  iron,  and 
act  exactly  as  the  permanent  magnet  does.  When 
remove  1  from  the  field  of  force  it  will  show  hardly 
any  magnetism.  If  a  piece  of  steel  is  treated  in  the 
same  way,  it  will  also  show  magnetism  when  in  the 
field  ;  but,  on  removal,  will  retain  some  of  it.  It  is 
a  permanent  magnet. 

Permanent  magnets  are  easily  made  of  such  mater-' 
ial.  The  bar  of  steel  should  be  of  good  quality, 
and  tempered  to  a  straw  color  or  purple.  All  the 
shaping,  filing  or  polishing,  which  it  is  proposed  to 
give  it,  should  be  done  before  magnetizing,  as  the 
least  thing  in  the  way  of  filing  or  jarring  the  mag- 
net injures  its  power. 


24 


ELECTRIC  TOT  MAKING. 


It  may  be  magnetized  by  another  magnet,  perma- 
nent or  electro  —  or  by  a  magnetizing  coil  and  bat- 
tery. It  is  enough  to  touch  one  end  to  the  most 
strongly  magnetic  part  of  the  field  magnet  of  an 
active  dynamo.  This  suffices  because  of  the  intense 
polarity  of  the  powerfully  excited  machine. 

With  a  single  permanent  magnet,  a  bar  may  be 
thus  magnetized.  It  is  rubbed  from  the  centre  to 
one  end,  with  one  pole  of  the  magnet  a  number  of 
times,  the  magnet  being  drawn  away  from  the 
end  and  carried  back  to  its  centre  through  the  air, 
and  the  stroking  is  r°peated  a  number  of  times.  Then 
the  same  process  with  the  other  pole  of  the  magnet 
is  applied  to  the  other  half  of  the  bar.  It  is  well  to 
turn  it  over  so  as  to  stroke  all  sides  of  it. 

A  simplerway  is  to  stroke  from  one  end  of  the  bar 
to  the  other,  always  in  the  same  direction,  with  one 
pole  of  a  magnet,  returning  it  through  the  air. 

Two  magnets  may  be  fixed  in  an  inclined  position 
with  their  poles  of  opposite  name  close  together,  and 
the  bar  may  be  stroked  with  them  as  described  above 
for  a  single  magnet.  The  next  cut  illustrates  this 
method  as  well  as  the  process  next  to  be  described. 


FIG.  4.    MAGNETIZING  A  BAR  OF  STEEL. 

An  excellent  method  is  to  apply  the  stroking  from 


MAGNETIZING  HORSESHOE  BARS.  25 

centre  to  ends  with  two  magnets  simultaneously.  A 
little  bit  of  wood  or  brass  should  be  used  to  prevent 
their  ends  from  coming  in  contact  in  the  centre  of 
the '  magnet.  The  cut  shows  the  arrangement,  I 
representing  the  separating  piece,  and  also  shows  the 
bar  resting  upon  the  opposite  poles  of  two  other  mag- 
nets. The  end  to  be  stroked  with  a  north  pole  should 
rest  upon  the  north  pole  of  a  magnet,  and  the  same 
applies  to  the  south  pole. 


FIG.  5.    MAGNETIZING  A  HORSESHOE  MAGNET. 

Magnets  are  generally  either  straight  or  horseshoe 
in  shape.  If  of  the  latter  description  they  may  be 
magnetized  by  touching  both  poles  to  opposite  poles 
of  a  dynamo  field  magnet.  It  should  be  noted  that 
this  will  reduce  for  the  moment  the  power  of  the 
dynamo.  Where  a  small  electro-magnet  is  at  hand 
the  stroking  process  may  be  applied  as  shown  in  the 
cut.  The  bent  bar  is  placed  against  the  poles  of  the 
excited  electro-magnet,  and  is  drawn  downwards  as 
shown  by  the  arrow.  This  is  repeated  a  number  of 
times  and  the  bent  bar,  after  each  stroke,  is  pulled 


26  ELECTRIC  TO  Y  MA  KING. 

away  from  the  electro-magnet  and  is  returned  to  its 
original  position.  It  is  then  well  to  reverse  opera- 
tions; to  apply  the  other  face  of  the  bent  bar,  now 
partly  magnetized,  to  the  electro-magnet,  but  this 
time  to  keep  the  bend  upwards  as  the  opposed  poles 
must  be  kept  in  the  same  relation.  The  bar  is  now 
drawn  upwards  and  away  from  the  electro-magnet  a 
few  times  and  the  operation  is  complete. 

If  the  electro-magnet  has  its  poles  too  far  apart  to  fit 
the  horseshoe  bar,  which  it  is  desired  to  magnetize, 
a  small  block  of  iron  can  be  placed  against  one  pole 
to  set  as  an  extension.  To  each  pole,  if  desired,  an 
extension  can  thus  be  attached  so  that  a  much  larger 
or  smaller  horseshoe  bar  can  be  magnetized. 

If  the  horseshoe  bar  is  thin  in  the  other  direction, 
so  that  its  edge  would  come  against  the  faces  of  the 
electro-magnet,  the  inside  or  outside  of  the  bar 
should  be  rubbed,  and  not  the  edges. 

To  make  powerful  magnets  thin  pieces  of  steel  may 
be  magnetized  separately  and  then  clamped  or  screwed 
together.  They  must  not  be  rivetted  or  soldered  as 
either  would  injure  the  magnetism. 

Another  way,  Jacobi's  method,  to  magnetize  a 
horseshoe  bar,  is  to  place  it  with  its  poles  against  those 
of  a  strong  horseshoe  magnet.  A  bar  of  soft  iron, 
long  enough  to  reach  across  from  outside  to  outside 
of  the  parallel  legs  is  now  laid  across  at  or  near  the 
ends  of  the  legs  of  the  bar  to  be  magnetized  and  is 
drawn  along  it  back  to  the  bend  and  away  from  it.  It 


MAGNETIZING  WITH  COILS.  27 

is  returned  through  the  air  and  the  process  repeated 
a  few  times  on  each  side  of  the  bar.  It  is  said  that  a 
one-pound  magnet  may  thus  be  made  which  will  carry 
twenty-six  and  a  half  pounds. 

To  magnetize  with  a  coil,  all  that  is  necessary  is  to 
surround  a  part  or  all  of  the  bar  with  a  coil  of  in- 
sulated wire  and  to  pass  a  strong  current  through  it 
for  an  instant.  By  Elius'  method  the  coil  is  moved 
backward  and  forward  along  the  bar  which  it  en- 
circles while  the  current  is  passing.  The  number  of 
passes  is  of  greater  importance  for  weak  currents.  For 
strong  ones  a  single  pass  is  ample. 

By  another  method  the  bar  is  armed  with  two  short 
cylinders  of  iron,  one  at  each  end  of  three  or  four 
times  its  diameter.  These  armatures  should  be  of  soft 
iron.  It  is  placed  in  the  axis  of  a  coil  that  is  of  the 
same  diameter  as  the  armatures  and  which  is  long 
enough  to  include  both  armatures  and  the  bar.  A 
current  is  passed  through  the  coil  and  powerful 
magnetization  results. 

To  preserve  magnets  their  opposite  poles  must  be 
connected  so  as  to  complete  the  magnetic  circuit. 
With  bar  magnets  this  is  best  done  by  placing  them, 
almost  touching  each  other,  in  pairs  with  their 
opposite  poles  corresponding  in  direction.  Two  little 
bars  of  soft  iron  laid  across  from  pole  to  pole  com- 
plete the  circuit.  Such  bars  are  termed  keepers.  If 
a  single  magnet  is  in  question  a  bent  piece  of  soft 
iron  may  be  used  to  connect  the  two  poles.  A  magnet 


•28  ELECTRIC  TOT  MAKING. 

may  even  be  left  without  any  keeper,  if  placed  in 
the  magnetic  meridian.  For  horseshoe  magnets  a 
single  keeper,  the  armature,  suffices  to  connect  both 
poles. 

In  using  magnets  all  jarring  must  be  avoided.  It  does 
no  harm  to  pull  the  armature  off  if  done  perfectly 
steadily  and  without  jar.  The  re-attraction  of  the 
armature  with  a  "  click,"  is  what  deteriorates  a  per- 
manent magnet  most  rapidly. 


FIG.  6.    THE  ROLLING 


Rolling   Armatures. 

The  rolling  armature  consists  of  a  short  cylindrical 
axis  of  iron  to  whose  center  a  wheel  is  attached.  The 
wheel  may  be  made  of  lead  or  other  metal.  When  it 
is  placed  as  shown  upon  a  horseshoe  magnet  it  will 
adhere,  but  if  the  magnet  is  properly  inclined  will  roll 
down  to  the  end.  The  momentum  of  the  fly-wheel 
keeps  up  the  motion  and  the  armature  rolls  across  the 


ROLLING  ARMATURES.  29 

poles  and  up  the  other  side  for  a  considerable  distance. 
A  modification  of  this  armature  con- 
sists of  two  little  bars  of  iron  with 
brass  rollers  attached  to  their  ends. 
They  are  placed  in  the  position  A, 
as  shown  in  the  dotted  lines  in  the 
cut.  On  approaching  them  with 
the  magnet  they  become  polarized 
both  in  the  same  sense  and  at  once 

FIG  ;~KBPULSION  repel    each    other    and  roll    away    as 


If  the  horseshoe  magnet  has  parallel  sides,  and  the 
last  described  armatures  are  nicely  made,  they  may  be 
made  to  roll  upon  it  somewhat  as  the  other  rolling 
armature  does. 

By  concealing  the  magnet  under  a  sheet  of  paper 
the  recession  or  rolling  away  from  each  other  of  the 
two  bars  may  be  made  to  seem  quite  mysterious. 
Mahomet's    Coffin. 

The  next  cut  shows  a  very  pretty  magnetic  experi- 
ment which  recalls  the  famous  unsupported  coffin  of 
Mahomet.  A  needle,  whose  point  may  be  broken  off, 
is  magnetized  by  a  few  strokes  with  a  magnet.  On 
drawing  it  by  a  thread,  as  shown,  over  the  poles  of  a 
horseshoe  magnet  so  as  to  bring  like  poles  over  each 
other,  it  will  lie  horizontally  and  motionless  in  the 
air,  sustained  by  an  invisible  force.  As  it  is  drawn 
forwards  and  from  the  further  side  of  the  horseshoe 
magnet  it  tends  to  follow  the  lines  of  force  and  rises 


ELECTRIC  TO  7 


along  the  line   of  an   arc   gradually  reaching    the 
position  shown. 

With  a  strong  magnet  and  a  little  bar  of  steel,  con- 

^ 


FIG.  8.    MAHOMET'S  COFFIN. 

tainea  in  a  miniature  coffin,  the  last  resting  place  of 
the  prophet  could  be  well  simulated. 

Magnetic   Jack-Straivs. 

Magnetic  jack-strnws  arc  an  interesting  modification 
of  the  time-honored 
game.  They  are  made 
up  of  a  set  of  jack- 
straws  to  each  of  which 
a  piece  of  iron  is  at- 
tached. They  may  be 
given  the  usual  shapes 
exactly  as  in  the  regular 


FIG.  9.    MAGNETIC  JACK-STRAWS 

straws  are  drawn  out  one  by  one. 


In  place  of  the  hook 
there  is  substituted  a 
magnet.  With  this  the 


THE  MAGNETIC  TOP.  31 

In  the  cut  a  simple  way  of  making  the  straws  is 
shown.  Short  pieces  of  iron  or  steel  wire  are  used. 
Some  have  little  blocks  of  wood  fastened  to  them; 
others  are  bent  and  twisted,  others  are  plain. 
Different  values  are  assigned  to  each  kind.  Each 
player  draws  out  straws  until  he  shakes  or  moves  one 
which  he  is  not  attempting  to  remove.  He  then  re- 
signs to  the  other  player.  This  is  kept  up  until  all 
are  withdrawn.  The  one  getting  the  highest  score,  as 
determined  by  adding  up  the  value  of  the  straws 
captured,  is  the  winner. 

The  Magnetic  Top. 

This  amusing  toy  is  easily  made.  A  bar  of  steel, 
suitable  for  the  spindle  of  such  a  top  as  shown,  is 
sharpened  at  one  end,  and  a  metallic  or  heavy  wooden 
disc  is  fitted  to  it.  The  best  method  of  attachment 
would  be  by  screwing,  or  by  a  couple  of  nuts,  one  above 
and  one  below  the  disc,  the  spindle  being-  threaded 
in  either  case.  The  combination  is  a  top.  Before 
putting  it  together  the  spindle  is  magnetized. 
All  shaping,  cutting  or  filing  must  precede  the  mag- 
netizing. 


FIG.  10.    THB  MAGNETIC  TOP. 


32  EL ECTRIC  TOT  MAKING. 

A  supply  of  short  pieces  of  iron  wire  is  required ; 
gome  of  these  are  bent  into  different  shapes,  circles, 
letter  S's,  etc;  others  are  straight.  When  the  top 
is  spun  by  the  fingers,  and  one  of  the  wires  is  placed 
on  the  table  against  its  point,  it  is  slowly  carried 
back  and  forth  in  the  most  curious  way.  It  is  well, 
to  make  it  appear  still  more  mysterious,  to  use 
cotton  or  silk  covered  wire. 

As  the  top  rotates,  the  wire  is  carried  by  a  sort  of 
friction-pulley  action  along  in  the  direction  of  its 
length.  As  its  end  reaches  the  point  of  the  top  it 
changes  sides  and  returns  as  ib  is  acted  on  by  the 
other  side  of  the  spindle,  and  thus  goes  back  and 
forth,  first  on  one  side  and  then  on  the  other  side  of 
the  top  as  long  as  it  spins. 

The  Magnetic  Pendulum. 

A  universal  joint  is  one  that  admits  of  movement 
in  all  directions.  The  construction  of  a  perfect 
joint  of  this  description  is  far  from  a  simple  matter. 

The  magnetic  pendulum  shows  how  a  magnet  can 
be  instrumental  in  producing  one. 

The  original  idea  of  the  apparatus  was  to  show  the 
rotation  of  the  earth  by  Foucault's  well-known  ex- 
periment. A  pendulum  has  fitted  to  the  upper  end 
of  its  rod,  a  piece  of  iron  with  smoothly  rounded 
upper  end.  This  is  suspended  from  a  magnet  by 
simple  attraction.  Such  a  pendulum  is  free  to  swing 


THE  MAGNETIC  PENDULUM. 


33 


in  any   or   all   planes  without    being   restrained   by 
torsion. 


FIG.  11.    THE  MAGNETIC  PENDULUM. 

It  is  therefore  peculiarly  well  adapted  to  be  used 
in  proving,  by  its  change  of  plane  of  oscillation,  the 
rotation  of  the  earth  upon  its  axis. 


34  ELECTRIC  TOT  MAKING. 

It  is  not  to  be  supposed  that  the  motion  is  without 
retardation  from  its  method  of  suspension.  The 
magnet  acting  upon  the  soft  iron  produces  a  damp- 
ing action  due  to  induced  currents.  The  ordinary 
frictkm  can  be  reduced  by  having  the  face  of  the 
magnet  as  smooth  as  possible,  by  weighting  the  pen- 
dulum until  it  is  barely  supported,  and  by  accurate 
finish  of  the  iron  top  of  the  pendulum  rod. 

It  is  obvious  that,  using  a  cylindrical  armature  with 
horizontal  axis,  the  pendulum  could  be  made  to 
swing  always  in  the  same  plane.  The  curvature  of 
the  cylindrical  surface  also  could  be  modified  so  as 
to  give  a  cycloidal  arc  of  swing  to  the  pendulum 
bob.  But  the  isochronisin  of  the  pendulum  would 
be  affected  by  the  action  of  the  magnet  on  the  iron, 
so  that  a  cycloidal  pendulum  might  not  prove  isochro- 
nous. 

Mayer's  Floating  Needles. 

This  is  an  exceedingly  pretty  experiment,  being  an 
improvement  on  the  well-known  magnetic  fishes.  A 
number  of  large  needles  are  magnetized,  all  in  the 
same  sense  as  regards  their  relation  of  poles  to  points 
or  eyes.  Each  needle  is  then  thrust  through  a 
small  cork,  so  that  only  a  little  bit  of  the  eye  endi 
projects  above  one  surface  of  the  corks.  They  are 
then  floated  in  a  vessel  of  water  as  shown,  the  like 
poles  coming  above  the  surface.  Under  the  effect 
of  repulsion  and  attraction,  they  float  into  the  most 
symmetrical  shapes,  some  of  which  are  shown  in  the 


MAGNETIC  NEEDLES. 


35 


lower  diagrams  of  the  cut.  To  cause  them  to  separate, 
a  magnet  pole  of  the  same  name  as  that  of  their 
upper  ends  may  be  brought  above  them.  This  re- 
pels them  in  all  directions. 


FIG.  12.    MAYER'S   MAGNETIC  NBEDLBS. 

These  floating  needles  are  due  to  Prof.  A.  M. 
Mayer,  of  the  Stevens  Institute,  N.  J.,  and  will  well 
repay  investigation. 

Magnetic  Fishes  and  the  Magnetic  Swan,  Boat,  etc. 

A  few  words  are  enough  to  describe  these  well- 
known  toys.  The  fishes  or  other  objects  are  m  ;de  of 
thin  block  tin  or  other  non-magnetic  material,  so 


36  ELECTRIC  TOY  MAKING. 

as  to  float  in  water.  Bits  of  iron  or  of  magnetized 
steel  are  secured  to  them  in  the  proper  places.  Thus, 
for  the  fish,  a  little  bit  of  iron  wire  projecting  from 
the  mouth  is  proper.  For  the  swan  or  boat  a  piece 
of  magnetized  steel  may  be  secured  in  a  similar  posi- 
tion. 

By  a  common  magnet  attached  to  a  thread  with  a 
little  stick  or  rod,  the  fish  may  be  caught.  The 
swan  and  boat  may  be  attracted  or  repelled  by  one  or 
the  other  poles  of  the  magnet. 

By  using  fish  to  which  different  values  are  assigned, 
or  by  having  the  number  stamped  upon  them  in  a 
concealed  place,  a  game  can  be  made  up.  Each 
player  should  catch  one  fish  at  a  time,  alternating 
with  the  others.  The  one  who  catches  those  aggrega- 
ing  the  largest  number  would  be  winner.  The  num- 
bers of  the  fish  should  be  concealed,  so  as  to  be 
visible  only  when  out  of  the  water.  Thus  each 
player  would  have  to  rely  on  chance  for  his  score. 


CHAPTER  III. 

ELECTRO-MAGNETS. 

CONSTRUCTION  OF  ELECTRO-MAGNETS — MAGNETIZ- 
ING COILS  —  THE  MAGIC  CIRCLE  —  MAGNETIC 
HEMISPHERES. 

Construction  of  Electro-Magnets. 

ELECTRO-MAGNETS  are  almost  universally  made  of 
the  horseshoe  type.  The  core  should  be,  for  simple 
sustaining  power,  thick  and  short.  The  cuts  through 
the  book  show  the  regulation  shapes  which  curiously 
enough  are  not  the  most  powerful.  The  core  is  very 
conveniently  made  in  three  pieces,  the  two  arms 
being  tapped  or  pinned  into  the  yoke.  A  simple 
piece  of  bent  iron,  as  shown  in  the  electro  magnet  in 
Figure  5,  will  suffice  for  the  full  core.  It  must  be, 
bent  into  U  shape  while  hot,  if  of  large  size. 

The  coils  may  be  wound  directly  on  the  core,  in 
which  case  it  is  well  to  wrap  the  latter  with  paper. 
Either  insulated  or  bare  wire  can  be  used.  If  the 
latter,  rigorous  care  must  be  taken  not  to  permit  con- 
tiguous windings  or  coils  to  touch  each  other,  and  a 


38  ELECTRIC  TOT  MAKING. 

wrapping  of  shellacked  paper  must  be  employed 
between  each  layer  of  the  windings. 

On  the  whole  insulated  wire  is  to  be  recommended. 
A  common  mistake  is  to  wind  too  much  wire  around 
the  legs.  The  proper  amount  and  size  is  a  matter  of 
calculation,  all  depending  upon  the  battery  to  be 
employed,  and  the  length  and  section  of  the  core  and 
its  material. 

The  windings  upon  both  legs  must  be  in  opposite 
directions.  After  winding  the  straight  portion  of  one, 
the  wire  may  be  carried  diagonally  across  the  inter- 
vening space  to  the  opposite  face  of  the  other  leg,  and 
the  winding  may  thus  be  continued. 

The  coils  may  be  made  separate  as  will  be  de- 
scribed, or  may  be  wound  upon  bobbins  and  thrust  on 
as  required. 

Nothing  is  gained  in  general  by  carrying  the  wind- 
ings around  the  bend. 


FIG.  13.    JOULE'S    ELECTRO-MAGNET. 

A  very  powerful  form  of  magnet  is  here  illustrated. 


SOLENOID  MAO  NETS.  39 

It  was  devised  by  Joule,  largely  on  experimental  bases, 
and  presents  an  excellent  example  of  a  highly  efficient 
electro-magnet. 

The  core  is  readily  made  by  filing  off  one  side  of  a 
piece  of  gas  pipe.  No.  1  shows  the  section  of  the 
core,  and  No.  2  shows  the'  complete  magnet.  Here  it 
will  be  observed  the  winding  is  carried  around  the 
bend. 

Electro-magnets  are  used  in  motors,  dynamos  and 
bells,  and  form  a  very  important  element  in  electric 
constructions.  Their  power  depends  on  the  current 
which  passes  around  them  and  on  the  number  of 
turns  of  wire  through  which  the  current  passes.  The 
lifting  power  in  other  words  is  proportional  to  the 
ampere  turns. 

Sometimes  a  straight  bar  is  used  as  the  core,  and 
sometimes  the  armature  is  dispensed  with,  and  the 
drawing  into  place  of  the  movable  core  by  the  fixed 
coil,  or  the  drawing  of  the  coil  by  the  fixed  core  is 
utilized.  Thus,  if  through  a  coil  of  wire  a  sufficiently 
intense  current  is  passed,  a  bar  of  iron  brought  into  or 
near  the  opening  of  the  coil  will  be  drawn  or  sucked 
in  like  a  plunger  into  a  cylinder. 

The  Litter  type  of  magnet  is  ordinarily  termed  a 
solenoid,  not  very  correctly  however.  It  was  used 
extensively  by  Dr.  Page  in  his  motors  in  the  early 
days  of  the  science.  It  is  said  that  very  powerful 
solenoid  magnets  were  exhibited  by  the  old-time 
lecturers,  some  sustaining  the  weight  of  several  men. 


40  ELECTRIC  TOY  MAKING. 

Any  magnetizing  coil  with  a  bar  of  iron  may  be 
used  to  illustrate  this  action.  The  drawing  up  of  a 
bar  from  the  table  into  its  axis  presents  an  extraor- 
dinary appearance  when  first  seen.  It  is  obvious  that 
another  version  of  Mahomet's  coffin  could  be  built 
upon  this,  the  core  being.held  down  by  a  fine  thread. 
This  could  be  made  to  present  the  appearance  of  a 
metal  bar  floating,  balloon  fashion,  at  the  end  of  a 
thread. 

The  winding  of  a  magnet  may  be  secured  in  place 
by  glue  or  varnish,  as  will  be  described  iinder  "Mag- 
netizing Coils  "  more  fully.  It  is  enough  to  wind  on 
all  the  wire  and  then  apply  glue  to  the  finished  coil, 
drying,  baking,  and  varnishing  or  painting. 

It  is  obvious  that,  if  a  single  length  of  wire  is  used 
for  winding,  and  if  the  legs  are  wound  separately,  one 
end  will  come  next  to  the  core,  and  the  other  end  will 
be  on  the  outside  of  the  wire  coils  and  on  the  other  leg. 
If  wound  separately  on  each  leg  and  afterwards  joined 
across  the  bend,  the  ends  of  the  wire  may  be  made  to 
come  out  symmetrically.  As  regards  appearance  it  is 
preferable  to  have  them  lie  next  the  iron  core;  for 
ease  of  repair  they  should  be  on  the  outside.  The 
latter  is  to  be  recommended. 

Magnetizing    Coils. 

The  construction  of  magnetizing  coils,  which  have 
no  core  to  support  or  carry  the  wire,  and  in  which 
the  wire  must  be  compact  and  adherent,  layer  to  layer, 


MAGNETIZING  COILS.  41 

>• 

requires  special  care.  They  are  wound  upon  a 
mandrel,  a  cylinder  generally,  which  is  afterwards 
withdrawn.  It  is  necessary  to  arrange  so  that  this 
withdrawal  will  be  possible;  therefore,  the  mandrel 
should  be  slightly  tapered,  if  possible,  to  facilitate  the 
removal.  A  glass  bottle,  a  tumbler,  or  a  round  ruler 
or  piece  of  curtain  roller  are  good  examples  of  man- 
drels. 


F  G.  14.    MAGNETIZING  COIL. 

To  make  a  magnetizing  coil  a  mandrel  of  any  con- 
venient material  is  selected.  A  piece  of  paper  is 
wrapped  around  it  and  on  this  the  insulated  wire  is 
wound  as  neatly  as  possible.  This  may  be  done  by 
hand  as  regularly  as  is  possible  on  a  lathe,  although 
the  use  of  the  latter  saves  time.  Where  there  are  a 
great  number  of  turns  of  wire  an  extemporized 
winder  can  easily  be  put  together  in  a  few  minutes, 
the  mandrel  being  usid  as  axle,  with  a  crank  handle 
attached  to  one  end,  and  then  mounted  in  a  couple 
of  standards. 

The  windings  of  the  coil  have  to  be  fastened  to- 
gether. For  this  purpose  carpenters'  glue  may  be 
employed.  The  glue  is  applied  to  each  layer  as  it  is 


42  ELECTRIC  TOY  MAKING. 

wound  and  when  the  last  layer  is  in  place  the  free  end 
of  the  wire  is  kept  strained  until  the  glue  has 
hardened,  which  should  be  in  an  hour.  The  whole 
can  then  be  slipped  off  the  mandrel  and  dried  over  a 
stove. 

If,  on  drying  it,  the  surface  shows  cracks,  they  can 
be  stopped  up  by  a  further  coating  of  glue,  followed 
by  drying. 

The  coil  thus  prepared  can  be  painted  or  varnished 
with  alcoholic  solution  of  shellac,  which  prevents  the 
glue  taking  up  moisture,  and  acts  to  hermetically  seal 
the  windings  of  the  coil. 

Additional  security  may  be  given  by  binding  with 
wire,  as  shown  in  the  cut,  but  this  is  unnecessary 
either  when  glue  is  employed  or  when  the  next  de- 
scribed method  is  adopted. 

A  much  nicer  and  more  effectual  way  is  to  use  a  so- 
lution  of  gum  copal  in  ether.  This  is  applied  to  layer 
after  layer  and  solidifies  the  whole  mass  with  a  water 
repelling  medium.  Alcoholic  solution  of  shellac  can 
be  used  in  the  same  way.  Heating  may  be  necessary, 
as  in  the  use  of  glue,  to  bring  about  the  last  degree 
of  solidification. 

The  Magic  Circle. 

The  magic  circle  next  illustrated  is  designed  for 
use  with  a  small  magnetizing  coil.  It  is  simply  two 
semi-circles  of  soft  annealed  iron,  provided  with  rings 
or  handles  exactly  at  the  centre  of  each  piece.  The 


THE  MAGIC  CIRCLE. 


4',} 


faces  are  planed  or  filed  off  so  as  to  fit  accurately.  A 
good  size  is  made  of  one  inch  round  iron,  bent  into  a 
circle  of  three  inches  internal  diameter.  For  such  a 
circle  a  coil  of  number  eighteen  to  twenty  wire,  wound 


Fio.  15.    THE  MAGIC  CIRCLE. 

into  forty  or  fifty  turns,  suffices.  With  a  current  of 
good  strength  the  attraction  the  circles  will  develop 
is  surprising. 

Magnetic  Hemispheres, 

A  very  peculiar  form  of  magnet  is  shown  in  the 
next  cut.  Although  a  modification  of  it  is  attributed 
to  Prof.  Forbes,  by  Thompson  in  his  recent  work  on 


44  ELECTRIC  TOT  MAKING. 

the  electro-magnet,  it  is  really  a  very  old  form.  The  cut 
is  a  reproduction  from  Davis'  Manual  of  Magnetism, 
a  work  copyrighted  in  1847.  It  may  aptly  be  termed 
the  Magdeburgh  Hemispheres  of  Electricity. 

The  small  sectional  figure  in  the  left  lower  corner 
shows  the  construction.     Two  cylinders  of  soft  iron 


FIG.  1G.    THB  MAGNETIC  HEMISPHERES. 

have  cut  out  an  annular  groove  of  size  adapted  to  re- 
ceive a  magnetizing  coil.  A  slot  is  cut  to  permit  the 
wires  to  come  out  where  the  two  halves  are  face  to 
face  and  in  contact. 

When  the  current  is  turned  on  and  passes  through 


MAGNETIC  HEMISPHERES.  45 

the  coil,  embedded  in  the  recess,  it  polarizes  the  two 
coils,  and  if  placed  together  they  are  strongly  at- 
tracted. No  magnetic  circuit,  it  will  be  observed,  is 
formed. 

The  coil  may  be  a  movable  one,  or  may  be  cemented 
in  place  with  varnish  or  sealing-wax.  Rings  should 
be  fitted  to  both  parts.  Two  persons  may  be  placed 
in  opposition  to  each  other  to  try  to  pull  them  apart. 
The  same  magnetizing  coil  may  be  used  for  these 
as  for  the  magic  circle.  The  metal  of  the  core  may  be 
a  little  heavier  than  that  shown  in  the  cut.  These 
show  very  little  residual  magnetism  and  fall  apart 
easily  when  the  current  ceases.  The  magic  circle, 
on  the  other  hand,  retains  much  residual  magnetism 
even  when  the  current  is  turntd  off. 

When  two  people  pull  against  each  other  in  their 
endeavors  to  draw  apart  the  halves  of  this  apparatus 
a  sudden  breaking  of  the  circuit  will  cause  a  sudden 
giving  away  or  perhaps  a  fall  backwards. 

The  residual  magnetism  of  the  magic  circle  is  so 
great  that  to  obtain  the  same  sudden  separation  a  re- 
versal of  the  direction  of  the  current  is  necessary. 
This  reversal  can  be  easily  made  by  shifting  the  ends 
of  the  wire  by  hand  so  as  to  connect  with  the  other 
poles  of  the  battery. 


CHAPTER  IV. 
ELECTRIC  MOTORS. 

PENDULUM  COIL  MOTOR — RECORDON  MAGNET  MOTOR 
—  MULT1POLAR  MOTOR — PAGE'S  ROTATING  ARMA- 
TURE— THE-  ELECTRIC  LOCOMOTIVE. 

Pendulum  Coil  Motor. 

A  VERY  pretty  form  of  slow  speed  motor  is  shown 
in  the  cut,  from  which  the  general  features  of  con- 
struction can  be  readily  understood.  A  permanent 
horseshoe  magnet  is  the  basis  of  c  .nstruction.  This 
is  attached  to  a  board,  as  shown,  so  as  to  be  held  an 
inch  or  so  above  its  surface. 

A  standard  rises  from  the  board  just  at  the  end  of 
the  m;ignet.  It  carries  a  horizontal  axis  on  which 
two  coils,  such  as  described  under  magnetizing  coils, 
swing  at  the  end  of  short  bars.  These  coils  encircle 
the  ends  of  the  magnet.  A  fly-wheel  is  carried  by 
two  other  standards  and  is  connected  by  pitmen  with 
suspension  rods  of  the  coils. 

The  coils  are  thus  connected  with  the  terminals  or 
binding-screws  seen  on  the  base. 

One  terminal  connects  by  the  standard  and  magnet 
itself  with  the  axis  of  the  fly-wheel.  A  projecting. 


PEND  UL  UM  COIL  MOTOR.  47 

segment  is  attached  to  this  axle,  which  extends  about 
one-third  around  the  shaft.  The  two  springs  seen 
rising  from  the  base  press  alternately  upon  this  as  the 
wheel  rotates. 

From  each  spring  a  wire  is  carried  up  the  large 
standard  and  down  one  of  the  vibrating  rods  to  a 
coil.  Each  coil  has  its  own  spring.  The  other  ends 


FIG.  17.    PENDULUM  COIL  MOTOR. 

of  the  coils  unite  and  pass  down   the  same  standard 
to  the  other  binding  post. 

Thus  the  current  entering  at  one  binding  post 
passes  by  way  of  the  magnet,  standards,  and  fly-wheel 
axle.  The  collar  is  almost  always  in  contact  with  one 
spring.  The  current  passes  through  this,  through 


48  ELECTRIC  TOY  MAKING. 

one  of  the  coils,  and  leaves  it  to  go  to  the  other  bind- 
ing post,  and  thence  to  the  battery  again.  The  coil 
is  attracted  towards  the  magnet  pole,  and  as  it  is 
drawn  thither  causes  the  wheel  to  rotate.  As  it 
reaches  the  pole  and  swings  beyond  it  the  collar 
breaks  the  connection  and  excites  the  other  coil  now 
most  removed  from  its  pole.  This  is  in  turn  attracted, 
keeping  up  the  rotation  of  the  wheel.  It  is  also 
clear  that  at  certain  phases  both  coils  may  be  excited, 
one  swinging  to  the  left  and  the  other  to  the  right. 
To  carry  this  out  two  collars  may  be  employed, 
one  for  each  coil.  The  other  construction  is  simpler. 

The  winding  of  the  coils  must  be  thus  arranged  : 
The  current  in  the  coil  surrounding  the  north  pole 
of  the  msignet  must  go  in  the  direction  contrary  to 
that  of  the  hands  of  a  watch,  if  the  observer  is  sup- 
posed to  be  looking  directly  at  the  magnet  end.  The 
current  in  the  other  coil  must  go  in  the  opposite 
direction. 

Finally,  the  permanent  magnet  might  be  made  of 
circular  section  so  as  to  more  closely  conform  to  the 
coils,  or  the  latter  may  be  wound  npon  a  square 
mandrel.  In  all  such  constructions  it  is  important 
to  keep  the  coils  near  to  the  field. 

This  motor  illustrates  one  of  the  solenoid  construc- 
tions already  alluded  to,  where  the  core  is  stationary 
and  the  coils  move.  It  is  further  to  be  noted 
that  two  round  cores  of  unmagnetized  iron  can  be 
used  instead  of  a  magnet.  In  such  case  the  direction 


REGORDON  MAGNET  MOTOR.  49 

of  winding  of  the  coils  is  a  matter  of  indifference. 
Recordon  Magnet  Motor. 

A  very  neat  motor  is  based  upon  the  same  type  of 
magnet  as  that  used  in  the  induction  coil  shown  on  a 
later  page.  In  the  present  illustration  B  represents 
such  a  magnet,  mounted  in  a  frame  and  provided 


FIG.  18.    RKCORDON  MAGNET  MOTOR. 


with  two  pole  pieces,  one  projecting  from  each  end. 
The  one  on  the  right  has  hinged  to  it  the  armature 
A.  The  other  pole  piece,  E,  is  so  shaped  as  to  admit 
of  the  armature  going  within  it,  and  making  as  close 
a  fit  as  compatible  with  the  absence  of  actual  contact. 
An  axle  with  fly-wheel  is  journaled  in  the  lower  part 


50  ELECTRIC  TOT  MAKING. 

of  the  frame.  On  the  axle  are  a  couple  of  commu- 
tator drums,  on  which  two  springs,  b  1),  press. 

The  two  commutators  are  of  insulating  material, 
wood  or  ebonite,  and  one-half  of  the  face  of  eacli  is 
coated  with  a  slip  of  brass,  which  connects  with  the 
axle. 

One  of  the  binding  screws,  by  a  short  piece  of  wire, 
connects  with  the  frame  of  the  apparatus,  with  the 
axle  of  the  fly-wheel  and  with  the  metallic  commuta- 
tor sectors.  The  other  binding  post  connects  with 
one  of  the  coil  terminals.  The  two  springs  are  in- 
sulated from  the  frame,  which  is  effected  by  using  a 
bar  of  wood  to  attach  them  to.  A  wire  soldered  to 
the  screws  which  attach  the  springs  thereto,  runs  back 
of  the  wood  to  the  other  coil  terminal.  The  wire 
must  be  insulated  from  the  frame.  A  pitman  is  at- 
tached to  the  free  end  of  the  armature,  and  its  other 
end  receives  the  crank  pin  of  a  crank  fastened  to  the 
fly-wheel  axle.  As  the  axle  rotates  the  armature  will 
rise  and  fall,  and,  as  the  armature  is  drawn  up  and 
down,  the  fly-wheel  will  rotate. 

The  commutators  are  so  adjusted  that  when  the 
armature  is  at  its  highest  point  the  springs  are  just  in 
contact  with  the  edge  of  the  metallic  segment.  This 
closes  the  circuit  and  the  armature  is  attracted  and, 
as  it  descends,  it  turns  the  crank,  axle  and  fly- 
wheel. It  is  clear  that  if  the  crank  turns  the  wrong 
way  the  circuit  will  at  once  be  broken.  For  this 
reason  the  wheel  should  be  started  in  the  right  direc- 


RECORDON  MOTOR.  51 

tion  by  hand.  The  armature  is  therefore  drawn  down 
by  the  magnet  as  long  as  contact  of  springs  and  com- 
mutator sectors  last.  This  ceases  just  as  the  arma- 
ture reaches  its  lowest  point.  The  momentum  of  the 
fly-wheel  completes  the  other  half  of  the  revolution, 
and  again  closes  the  circuit  through  the  commuta- 
tor just  as  the  highest  point  is  reached  by  the  arma- 
ture. 

The  same  is  repeated  over  and  over  again,  and  the 
wheel  is  kept  rotating  as  if  by  a  single  acting  engine. 

It  is  in  some  respects  well  to  set  the  commutator 
so  that  connection  will  be  made  only  after  the  arma- 
ture has  descended  a  very  short  distance.  This  will 
make  the  motor  less  apt  to  start  in  the  wrong  direc- 
tion. 

The  extension  of  the  pole  pieces  gives  the  magnet 
a  long  range  of  action.  The  shape  is  also  very  com- 
pact, and  the  motor  suggests  possibilities  in  the  way 
of  improvement.  The  armature  might  be  wound 
Avith  wire  and  thus  be  excited  also  so  as  to  increase 
the  attraction.  • 

M.  Recordon,  it  is  to  be  noted,  makes  these  mag- 
nets with  hollow  cores.  The  aperture  can  be  seen  in 
the  cut  just  back  of  the  left-hand  pole  piece. 

Multipolar  Motor. 

One  of  the  principal  points  of  merit  in  a  well 
designed  motor  is  the  absence  of  dead  points.  The 
multipolar  motor  shown  in  the  next  illustration, 


52 


ELECTRIC  TOT  MAKING. 


while  it  has  such,  on  account  of  their  being  subdi- 
vided into  six  for  each  revolution,  is  very  constant  in 
its  movement. 

The  annular  frame,  A,  and  base,  F,  must  be  made  of 


Fio.  19.    MULTIPOLAK  MOTOR. 


some  non-magnetic  material,  such  as  brass  or  wood. 
Through  the  frame,  at  even  distances,  six  bars,C,  C, 
of  iron  are  thrust. 

These  constitute  armatures.     The  rotating  field  is 


MULTIPOLAR  MOTOR.  53 

built  upon  a  drum,  D,  which  carries  six  equally 
spaced  radiating  cores,  carrying  coils  of  wire,  B,  B. 
D  may  be  made  of  brass  or  even  of  wood.  A  non- 
conducting or  insulating  collar,  E,  surrounds  one 
part  of  it.  The  latter  collar,  E,  is  designed  to  re- 
ceive upon  its  surface  one  set  of  terminal  wires  from 
the  magnetizing  coils  ;  the  other  terminals  go  to  the 
surface  of  the  drum,  D. 

The  magnetizing  coils  are  wound  very  solidly  with 
insulated  wire  upon  the  six  cores.  They  may  be 
further  secured  by  flanges  pinned  or  screwed  in 
place,  as  the  centrifugal  force  will  be  considerable. 

The  connections  of  the  six  field  magnets  are  ar- 
ranged to  carry  out  this  principle.  During  one-half 
of  the  total  time  of  a  rotation  they  must  be  receiving 
current,  but  this  again  must  be  divided  into  six 
periods,  which  amounts  to  saying  that  they  are  to  be 
excited  during  alternate  twelfths  of  each  revolution. 
When  in  the  position  shown  in  the  cut  they  are  not 
excited.  After  they  rotate  until  one-twelfth  of  a 
revolution  is  accomplished,  the  magnet  cores-are  half 
way  betAveen  the  outer  cores  or  armatures.  At  this 
point  they  are  excited  and  the  current  continues  for 
the  next  twelfth  of  a  revolution,  to  cease  again  as  the 
magnets  pass  the  armatures.  This  is  "kept  up  all 
around  the  circle. 

The  six  wires  carried  to  the  collar,  E,  connect  with 
a  brass  or  copper  ferrule  thereon.  Six  wires  or  ribs 
soldered  to  the  ferrule  at  equal  distances  apart  lie 


54  ELECTRIC  TOT  MAKING. 

upon  the  surface  of  the  collar.  A  copper  spring 
rising  from  the  base  presses  upon  these.  The  pro- 
portions are  so  adjusted  that  the  spring  presses  upon 
each  wire  during  one-twelfth  of  a  revolution.  This 
contact  period  must  correspond  to  the  period  when 
the  magnets  pass  from  the  central  point  between 
armatures  to  the  point  opposite  the  same. 

The  other  six  wires  run  to  a  ferrule  upon  the 
drum  D.  A  second  spring  presses  continually  upon 
this  ferrule. 

The  wires  from  the  battery,  or  other  source  of 
current,  connect  with  the  two  springs,  one  wire  with 
each. 

If  the  arrangement  thus  described  is  studied  it  will 
be  seen  that  the  current  pas-es  during  contact  of  the 
spring  with  the  ribs  upon  the  collar,  E,  or  during  the 
proper  portions  of  the  revolution.  The  magnets 
are  all  simultaneously  excited  in  parallel,  and  are 
attracted  to  the  cores  in  advance,  referred  to  the 
direction  of  their  motion.  As  soon  as  they  reach 
them  the  current  ceases  and  their  inertia  carries  them 
through  the  next  sixth  of  a  revolution,  when  they 
are  again  excited. 

The  speed  such  a  motor  will  attain  is  very  great, 
and  hence  special  care  has  to  be  taken  to  guard 
against  centrifugal  force  displacing  the  coils. 

Any  number  of  magnets  may  bo  employed  with  a 
corresponding  number  of  armatures  and  commutator 
connections,  as  the  ribs  are  termed.  It  will  be  found 


COMMUTATOR  FOR  MULTIPOLAR  MOTOR.     55 

that  the  height  as  well  as  breadth  of  the  ribs  is  a 
factor  in  determining  the  period  of  contact.  The 
more  elegant  way  is  to  make  each  rib  exactly  one- 
sixth  the  circle  in  width  and  fill  the  space  between 
the  ribs  with  insulating  material  flush  with  the  sur- 
face of  the  ribs,  so  as  to  form  a  true  cylindrical  sur- 
face for  the  spring  to  bear  against. 

The  next  cut  shows  in  general  the  plan  of  connec- 
tion, only  for  seve,n  instead  of  for  six  magnets.    At  M  is 


FIG.  20.    COMMUTATOR  OP  MULTIPOLAR  MOTOR. 

the  ferrule  upon  the  drum,  against  which  one  spring, 
C,  is  constantly  pressing.  F,  F,  represent  the  ribs 
connected  to  the  collar,  against  which  ribs  the  other 
spring,  D,  bears.  Their  degree  of  projection,  it-  will 
be  seen,  determines  the  time  of  contact.  P  and  N 
are  the  wires  from  the  battery,  and  B  is  the  base- 
board. The  dotted  lines,  H,  H,  indicate  the  course 
of  two  of  the  wires  running  to  and  connected  with 
the  ferrule,  M. 

A  modification  of  this  motor  should  be  here  alluded 
to.     The  magnets  are  made  stationary  and  occupy 


56  ELECTRIC  TOT  MAKING. 

the  position  of  the  armature  bars,  while  the  rotating 
portion  carries  only  the  six  armature  bars.  The 
commutator  bars,  springs,  and  ferrules  are  identical. 
One  set  of  terminal  wires  from  the  magnets  are  united 
and  a  single  larger  wire  is  carried  to  a  binding  post. 
The  other  ends,  in  like  manner,  connect  with  one  of 
the  springs.  The  other  spring  connects  to  the  other 
binding  post.  Or  all  the  ends  of  the  magnet  wires, 
except  those  of  any  two  magnets  nexb  to  each  other, 
may  be  connected  so  as  to  bring  the  magnets  in  series. 
The  two  free  ends  are  connected  as  described,  by 
means  of  the  springs,  one  to  the  commutator,  or 
ferrule,  and  the  other  to  the  binding  post. 

Page's  Rotating  Armature. 

A  simple  form  of  motor,  which  may  attain  very 
high  speed,  is  shown  in  the  cut.  The  great  velocity 
of  an  electric  motor  is  not  to  be  considered  an  advan- 
tage, as  it  necessitates  a  reduction  of  speed  by  belts 
and  pulleys,  or  their  equivalent. 

Upon  a  fixed  base,  a  permanent  U-shaped  magnet, 
N,  S,  is  secured,  above  which  a  horizontal  fixed  piece 
is  supported,  forming  the  top  member  of  a  suitable 
frame.  A  set-screw,  with  a  conical  hole  in  its  end, 
passes  through  the  centre  of  this  piece.  A  support, 
corresponding  to  the  set-screw,  is  secured  to  the  base 
directly  below  it,  as  shown.  This  support  is  a  pin 
with  a  conical  hole  drilled  in  its  top.  Between  the 
two  coned  supports  a  vertical  spindle  is  carried.  By 


PAGE'S  ROTATING  ARMATURE. 


57 


the  set-screw  the  adjustment  can  be  carried  out,  so 
as  to  leave  the  spindle  free  to  turn,  yet  without  any 
end  shake. 

To  the  spindle  is  attached  a  heavy  bar  of  iron,  wound 
with  insulated  wire,  which  is  virtually  a   U-shaped 


FIG.  21.    PAGE'S  ROTATING  ARMATURE. 

electro-magnet.  The  wire  is  all  wound  in  the  same 
direction.  The  ends  of  the  wire  are  carried  to  two 
divisions,  i  h,  of  a  two-part  commutator,  which  is 
attached  to  the  spindle  directly  above  the  rotating 


58  ELECTRIC  TOT  MAKING. 

magnet,  or  polarized  armature,  as  it  might  be  called. 
Two  springs,  g,  f,  of  copper,  brass,  or  silver,  press 
against  the  commutator.  Each  spring  is  attached 
to  the  frame,  and  each  has  its  own  binding  post  to 
receive  the  wires  of  the  actuating  circuit.  When  the 
current  passes  the  armature  and  spindle  rotate. 

While  the  construction  of  the  commutator  is  clear 
from  the  perspective  view,  a  small  sectional  repre- 
sentation is  also  given.  In  it  A  is  the  section  of  the 
vertical  spindle.  S,  S  are  the  two 
parts  of  the  commutator.  They 
consist  of  bent  plates  of  copper, 

Fiu.  22.    TWO-PART  .  rr. 

COMMUTATOR.  or  brass,  or  silver,  which  are  in- 
sulated from  the  spindle.  This  insulation  may  be 
simply  a  perforated  bit  of  wood  to  which  the  plates 
are  cemented  by  sealing-wax,  with  a  winding  of  silk 
at  the  ends  of  the  plates  to  further  secure  them.  The 
plates  must  of  course  not  touch  each  other,  and  are 
arranged  with  the  two  separations  almost  in  the  plane 
at  right  angles  to  the  plane  of  the  electro-magnet. 
In  the  diagram,  W,  W  represent  the  springs. 

The  general  action  of  the  motor  is  the  following  : 
The  current,  entering  by  uiie  binding  posts  and  springs 
through  the  commutator,  magnetizes  the  core  of  the 
electro-magnet,  which  is  generally  denominated  the 
armature.  The  magnetization  is  such  that  it  is 
attracted  in  one  direction  or  the  other,  assuming  that 
the  bar  does  not  lie  in  the  plane  of  the  magnet. 
Yielding  to  the  attraction  it  turns  on  its  axis  and 


THE  ELECTRIC  LOCOMOTIVE.  59 

swings  past  the  poles.  As  it  does  this,  each  spring 
presses  on  the  other  leaf  or  plate  of  the  commutator. 
This  causes  a  current,  the  reverse  of  the  preceding,  to 
pass  through  the  coil,  and  the  bar  is  at  once  repelled. 
As  its  momentum  has  carried  it  past  the  poles  of  the 
magnet  it  continues  its  rotation,  and  is  attracted  by 
the  distant  as  well  as  repelled  by  the  nearer  poles. 
The  same  action  of  reversal  occurs  twice  in  each  revo- 
lution. 

If  the  armature  lies  in  the  plane  of  the  fixed  mag- 
net the  motor  will  not  start,  but  a  touch  of  the  finger 
will  suffice  to  set  it  going. 

The  name  given  to  this  apparatus  is  that  of  the 
celebrated  Dr.  Page,  who,  about  half  a  century  ago, 
endeavored  to  introduce  electric  motors.  As  he  had 
no  cheap  source  of  current  his  work  was  a  failure. 
If  the  armature  in  this  motor  is  turned  by  power  it 
will  generate  a  current ;  in  other  words,  the  mechan- 
ism is  reversible. 

The  Electric  Locomotive. 

An  electric  locomotive,  babfed  on  the  use  of  a  motor 
such  as  already  described  under  the  title  of  "  Page's 
Rotating  Armature"  (page  56),  is  illustrated  here. 
The  general  construction  is  clear  from  inspection  of 
the  elevation.  The  motor  is  carried  horizontally  on 
a  little  car  moving  on  a  railway,  and  a  prolongation 
of  its  shaft  has  on  it  a  worm  which  gears  into  a 


GO 


ELECTRIC  TOT  MAKING. 


worm-wheel  on  the  axle  of  one  pair  of  Avheels.  This 
pair  of  wheels  is  attached  rigidly  to  the  axle  and  con- 
stitute 1ho  drivers. 


THE  ELECTRIC  LOCOMOTIVI 


The  current  is  taken  from  the  rails,  the  motor  act- 
ing as  a  bridge  across  them.  The  necessary  connec- 
tions for  carrying  out  the  plan,  and  the  arrangements 
for  automatically  reversing  the  engine,  will  be  under- 
stood from  the  view  showing  the  bottom  of  the  plat- 
form, the  wheels  and  reversing  blocks. 


ELECTRIC  LOCOMOTIVE.  61 

One  pair  of  wheels,  those  on  the  left,  are  mounted 
loosely,  the  axle  not  rotating.  The  central  or  darkly 
shaded  part,  M,  of  the  axle,  is  of  wood.  A  wire  from 
the  metallic  end  of  the  axle,  on  which  the  wheel,  K, 
rotates,  runs  to  a  central  plate,  and  thence  to  a  plate, 
G,  which  plates  are  insulated.  Near  Gr  are  two  plates, 
E  and  F,  also  insulated,  except  that  from  each  of 
them  a  commutator  spring,  to  supply  current  to  the 
motor,  rises. 

It  is  unnecessary  to  describe  the  springs  and  com- 
mutator. They  are  identical  with  those  already 
described  and  illustrated  (pages  56  to  59). 

An  insulated  switch,  A,  turns  about  the  central 
point  between  E  and  F.  To  its  pivot,  also  insulated, 
a  wire  is  attached,  which  connects  with  the  journal 
of  the  car-wheel,  J.  The  other  car- wheel  on  the  same 
axle  is  insulated  from  it  by  a  wooden  or  vulcanite 
piece  at  L. 

To  the  switcn  pivot  a  stiff  wire  with  contact  piece, 
C,  is  soldered.  This  presses  upon  E  or  F,  according  to 
the  way  the  switch  handle  is  turned.  To  the  switch 
handle  a  second  wire  is  soldered,  which  is  bent  so  as 
to  bring  its  two  contact  pieces,  B  and  D,  into  the 
relations  shown. 

Both  these  wires  must  be  of  spring  temper  to  ensure 
electrical  contact  by  pressure  between  their  ends  and 
the  plates  over  which  they  slide. 

The  moving  of  the  switch  handle  towards  the  part 
corresponding  to  the  lower  portion  of  the  cut  would 


62  ELECTRIC  TOY  MAKING. 

shift  the  contact  pieces,  B  and  C,  to  the  reverse  posi- 
tion, as  regards  the  plates  E  and  F.  C  would  be 
shifted  to  E,  and  B  would  be  shifted  to  F  ;  while  D 
would  slide  along  its  plate,  G-,  it  would  not  leave  it. 

As  the  switch  is  shown  in  the  cut  the  current 
would  enter  by  the  wheel,  K.  It  would  pass  to  the 
plate,  Gf,  thence  to  the  plate,  E.  It  would  then  go 
through  the  coil  of  the  armature  of  the  motor,  and, 
leaving  it,  would  go  through  the  plate,  F,  contact 
piece,  C,  switch  journal,  and  its  connection  to  the 
journal  of  the  wheel,  J,  and  through  that  wheel  to 
the  other  rail. 

This  causes  the  motor  to  rotate  and  propels  the  car 
along  the  track  always  in  the  same  direction. 

Now,  if  the  switch  is  turned,  as  already  described, 
so  as  to  reverse  the  position  of  the  contact  pieces,  C 
and  B,  this  will  reverse  the  direction  of  the  current 
as  it  goes  through  the  motor,  and  will  reverse  the 
direction  in  which  the  car  travels. 

This  reversal  may  be  automatically  effected  by 
switch  blocks  attached  to  the  roadway,  two  of  which 
are  indicated  in  the  plan  by  H  and  I.  If  such  are  to 
be  used  a  pin  is  inserted  in  the  end  of  the  switch, 
A,  shown  in  the  plan  and  elevation,  which  strikes 
the  inclined  edge  of  the  switch-blocks  and  shifts  over 
the  switch.  In  an  instant  the  motor  is  brought  to 
rest  and  then  starts  back  reversed. 

The  battery  connections  are  shown  in  the  eleva- 


LOCOMOTIVE  SWITCH  CONNECTIONS.         63 


G4  ELECTRIC  TOT  MAKING. 

tion.  The  rails  must  be  continuous,  or  must  have 
their  abutting  ends  connected  by  plates  or  wires. 
The  two  lines  of  rail  must  be  well  insulated  from  each 
other. 

Any  motor  may  be  used  to  drive  an  electric  loco- 
motive. The  advantage  of  those  working  with  a  per- 
manent magnet  for  field  is  that  they  have  a  fixed 
direction  of  movement. 

The  elevation  shows  several  details  not  needing 
description,  such  as  the  set-screws  for  adjusting  the 
end  play  of  the  armature  axle. 

The  general  system  of  reversing  might  be  applied 
to  any  other  fixed  direction  motor.  One  advantage 
of  the  automatic  reversing  is  that  it  obviates  the 
necessity  of  a  circular  or  continuous  track.  An  im- 
provement would  also  be  to  start  a  short  up-grade 
directly  beyond  the  reversing  block  to  aid  in  stopping 
and  starting  back  the  motor. 


CHAPTER  V. 

ELECTKIC   BELLS. 

THE    TOLLING    BELL — THE    VIBRATING    BELL — THE 
SAFE  PROTECTOR. 

The  Tolling  Bell 

ELECTRIC  bells  are  generally  of  the  gong  type,  and 
produce  a  sharp  ring.  The  cut  shows  how  a  large 
regulation-shape  bell  can  be  made  to  toll  by  an  elec- 
tric current.  In  many  cases  the  use  of  a  gong  would 
be  disagreeable  from  its  sound  or  appearance.  In 
the  arrangement  illustrated,  the  ringing  apparatus  is 
all  contained  within  the  cavity  of  the  bell  so  as  to  be 
pretty  well  hidden  from  sight. 

The  magnet  consists  of  a  perforated  iron  bobbin 
with  heavy  end  flanges,  of  the  Recordon  type.  A 
couple  of  pole  pieces  may  be  attached  to  the  ends  as 
shown.  The  magnet  is  attached  to  the  base  of  the 
bell.  One  of  its  terminal  wires  runs  through  the  axis 
of  the  extension  of  the  magnet  core  to  the  outside  of 
the  bell,  being  insulated  from  the  metal.  This  obvi- 
ates the  necessity  of  drilling  a  special  hole  in  the 
bell,  and  possibly  impairing  its  tone.  The  other 
terminal  wire  connects  directly  with  the  metal  of  the 
bell.  A  rod,  bent  into  an  irregular  IT  shape,  carries 


66 


ELECTRIC  TOT  MAKING. 


at  one  end  an  iron  ball,  and  constitutes  the  clap- 
per. To  the  other  limb  of  the  rod  a  flat-faced  bar  of 
iron,  long  enough  to  reach  from  outside  to  outside  of 
the  pole  pieces,  is  fastened.  This  acts  as  armature. 
The  bent  bar  is  pivoted  near  its  centre,  as  shown. 


FIG.  25.    TUB  TOLLING  BKLL. 


A  circle  or  ring  is  comprised  within  it  at  the  top  of  the 
bend,  which  opening  contains  the  suspension  rod  or 
core  extension  of  the  magnet.  One  pin  goes  through 
both  sides  of  the  ring  and  the  suspension  rod  in 


THE  TOLLING  BELL.  67 

question.     This    acts  as   a  very   excellent  pivoting, 
preventing  lateral  shake. 

The  bell  is  hung  to  a  metallic  bracket.  From  the 
battery  one  wire  runs  directly  to  the  bracket.  It 
thus  connects  with  the  magnet  coil,  through  the 
metal  of  the  bracket  and  bell. 

The  other  wire  from  the  battery  runs  to  a  key, 
whence  another  wire  connects  with  the  magnet  ter- 
minal wire  coming  out  of  the  bell  spindle. 

The  key  may  be  of  the  simplest  construction,  as 
shown  in  the  cut.  When  it  is  depressed,  thus  closing 
the  circuit,  the  magnet  is  excited,  attracts  its  arma- 
ture and  rings  the  bell. 

The  peculiar  form  of  the  magnet  is  not  only  advan- 
tageous in  compactness  of  shape  but  is  also  supposed 
to  give  better  results  than  usual  in  the  way  of  at- 
tractive power. 

The  Vibrating  Bell 

The  continuously  ringing  bell  is  one  which  will 
automatically  ring  as  long  as  the  current  continues. 
It  is  really  a  motor.  A  simple  form  is  shown  in  the 
cut. 

To  a  base-board  is  attached  an  electro-magnet.  A 
bar  of  soft  iron,  which  is  its  armature,  is  carried  by  a 
flat  spring  which  draws  it  away  from  the  magnet.  A 
contact  screw  is  so  arranged  as  to  touch  the  armature 
spring  when  the  armature  is  drawn  away  from 
the  magnet.  To  the  armature  is  attached  a  wire, 


ELECTRIC  TOY  MAKING. 

carrying  a  ball,  which  serves  as  a  clapper.  A  gong  is 
fastened  by  its  central  post  to  the  same  base-board, 
which  also  may  carry  two  binding  posts. 


Fio.  26.    THE  VIBBATING  BELL. 
The  connections  are  shown  in  dotted  lines.     From 


THE  SAFE  PROTECTOR.  69 

one  binding  post  a  wire  runs  directly  to  one  of  the 
magnet  terminals.  From  the  other  terminal  of  .the 
magnet  the  wire  connects  with  the  armature  spring. 
From  the  other  binding  post  a  wire  runs  to  the 
metallic  support  of  the  contact  screw. 

When  no  current  passes,  the  armature  is  drawn 
back  from  the  bell,  and  the  spring  is  in  contact  with 
the  contact  screw.  If,  now,  a  current  is  caused  to  pass, 
it  enters  by  one  of  the  binding  screws  and  excites  the 
magnet,  its  course  going  through  the  spring  and  con- 
tact screw.  The  magnet  attracts  its  armature,  and 
opens  the  circuit  by  drawing  the  spring  away  from 
the  contact  screw.  The  attraction  of  the  armature 
draws  the  clapper  against  the  bell  and  gives  a  ring. 
As  the  circuit  is  opened  the  armature  springs  back 
and  again  closes  the  circuit.  Again  the  armature  is  at- 
tracted and  the  bell  rings.  This  operation  is  repeated 
over  and  over  again  as  long  as  the  current  is  kept  up. 

The  usual  way  of  turning  on  the  current  is  by  a 
press-button,  which  construction  is  so  simple  as  to 
need  no  description.  It  is  seen  in  section  on  the  left 
hand  of  the  cut  on  page  66.  Any  form  of  switch 
will  answer  the  same  purpose. 

The  Safe  Protector. 

This  apparatus  is  what  may  be  termed  a  combined 
electrical  and  mechanical  safe  protector.  The  illus- 
tration shows  its  application  and  principle. 

In  Fig.  2  the  ordinary  bell,  such  as  described  in  its 


70 


ELECTRIC  TOY  MAKING. 


proper  place  (page  67),  with  battery,  switch-box  or 
"thief  detector/'  and  safe  are  shown.  From  the 
safe  two  wires,  I  J,  are  carried  to  the  switch-box. 
Within  the  safe  is  a  spring-switch,  which,  when 
pressed,  maintains  an  open  circuit,  and  when  released 


FIG.  27.     THE  SAFE  PROTECTOR. 


by  the  opening  of  the  safe  door,  closes  the  circuit. 
Such  a  switch  is  so  simple  that  enlarged  description 
is  not  required.  This  switch  is  actuated  by  the  safe 


THE  SAFE  PROTECTOR.  71 

door.  When  closed,  the  door  keeps  the  circuit  open 
by  pressing  on  the  switch.  When  the  door  is  opened  the 
circuit  closes,  as  the  gwitch  is  released  from  pressure. 

Two  wires  from  the  battery  and  bell  circuit  lead  to 
the  switch-bo*x,  connecting  with  the  binding  screws, 
E,  F,  Fig.  1,  on  top  of  the  box,  A  B  C  D.  Within 
the  box  each  wire  bifurcates  as  shown,  and  has  its  two 
terminals  connected  to  the  two  pairs  of  pins,  O1,  3 
and  0,  4  respectively.  On  the  pins,  0,  O1,  two 
springs,  R,  R1,  work,  to  whose  outer  ends  the  safe 
wires  are  attached.  These  wires  draw  the  springs 
down  until  they  press  against  the  steady-pins  1 
and  2. 

If,  now,  the  safe  is  opened  the  circuit  closes  and  the 
bell  rings.  If  the  burglar,  before  opening  the  safe, 
noticing  the  wires,  I,  J,  cuts  one  of  them  to  secure 
himself  from  detection,  the  spring  R  or  R1,  as  the 
case  may  be,  springs  up  and  makes  contact  with  the 
stud,  3  or  4,  on  the  opposite  bell  and  battery  terminal. 
This,  of  course,  closes  the  circuit,  also,  and  the  bell 
rings.  The  same  is  the  case  if  both  wires  are  cut. 
Both  springs  then  fly  up  and  the  circuit  is  closed  just 
as  before. 

It  will,  of  course,  be  an  object  to  hide  the  switch- 
box,  because  if  one  or  both  of  the  leads  from  bell  and 
battery  are  severed,  the  apparatus  will  become  inop- 
erative. The  wires,  I,  J,  must  also  be  so  fixed  as  to 
appear  like  ordinary  electric  leads.  They  must  be 
perfectly  free  for  their  entire  lengths. 


72  ELECTRIC  TOY  MAKING. 

If  the  burglar  understood  the  construction  all  he 
would  have  to  do  would  be  to  secure  the  wires,  I  J, 
by  staples  or  by  tying,  and  theu  to  cut  them  off  be- 
low the  staples.  This  would  prevent  the  bell  from 
ringing  and  would  enable  the  safe  to  be  opened.  It 
is  assumed,  however,  that  the  natural  course  of  cut- 
ting one  or  both  of  the  wires  will  be  followed  by  any 
illicit  operator,  who  attempts  to  prevent  the  electric 
alarm  from  operating. 


CHAPTER  VI. 
MISCELLANEOUS  TOYS. 

THE  ELECTRIC  DANCER — THE  MAGIC  DRUM — THE 
ELECTRIC  HAMMER  —  ELECTRIC  INSECTS — THE 
INCANDESCENT  LAMP. 

The  Electric  Dancer. 

THIS  amusing  toy  originally  was  produced  to  be 
operated  entirely  by  hand.  The  electrical  modifica- 
tion is  based  upon  the  principle  of  the  vibrating  bell, 
and  needs  but  a  short  description.  The  cuts  show 
one  construction  very  clearly. 

A  box  contains  the  motive  mechanism.  This  con- 
sists of  an  electro-magnet  with  a  soft  iron  armature 
carried  by  a  spring.  A  wire  from  the  battery  goes 
directly  to  the  magnet.  The  other  terminal  of  the 
magnet  connects  with  the  armature  spring  at  L1. 
The  other  end  of  the  spring  is  bent  at  right  angles 
at  L2,  and  carries  a  platform  on  a  support  L3.  This 
is  the  dancing  platform.  A  contact  spring,  S  S,  is 
carried  by  the  armature  spring.  A  contact  screw,  C, 
is  adjustable  as  regards  its  contact  with  the  spring 
S  S.  From  it  a  wire  runs  to  the  binding  post,  B,  to 
which  the  other  battery  wire  is  attached. 


74  ELECTRIC  TOT  MAKING. 

The  magnet  may  have  as  cores  round  iron  bars  f 
inch  in  diameter,  1£  inch  long,  and  wound  to  1£ 
inch  diameter,  with  No.  26  silk  covered  wire. 


FIG.  28.    THE  ELECTRIC  DANCER.    ELEVATION. 

The  action  of  a  current  on  such  mechanism  is  to 
keep  the  platform  in  constant  vibration,  which  may 


THE  ELECTRIC  DANCER.  75 

be  regulated  and  modified  over  quite  a  range  of  action 
by  the  screw,  C. 

The  figure  is  made  of  wood,  with  very  loose  joints, 
and  is  suspended  by  a  curved  arm,  so  that  its  feet 


A 

8 

© 

®  o 

C 

D 

FIG.  29.    THE  ELECTRIC  DANCKB.    PLAN. 

just  touch  the  stage.  When  a  current  passes,  the 
lignre  begins  to  dance,  and  keeps  it  up  as  long  as  the 
battery  supplies  enough  energy. 

Another  way  of  working  it  is  to  make  the  figure 
do  the  making  and  breaking  of  the  circuit.  For 
this  end,  the  binding  post,  B,  should  be  connected  to 
the  curved  suspension-rod,  instead  of  connecting 
with  the  contact  screw,  C.  Jointed  wires  are  carried 
through  the  figure,  and  the  ends  are  soldered  to  light 
brass,  or  copper  plates,  on  the  soles  of  the  feet.  The 
armature  spring  is  in  electrical  contact  with  the  top 
of  the  dancing  platform,  which  must  have  a  metallic 
surface.  Very  thin  sheet  brass,  or  copper,  may  be 
used  for  this. 

In  the  last  construction,  the  screw,  C,  and  spring, 


76  ELECTRIC  TOT  MAKING. 

S  S,  may  be  retained,  but  there  must  be  no  connec- 
tion between  them  and  the  binding  post,  B. 

Tims  arranged,  the  feet  will  make  and  break  the 
circuit.  The  jointed  wires  of  one  side  are  shown  in 
the  cut.  The  height  must  be  accurately  fixed,  so  that 
only  slight  adjustment  need  be  made  by  the  screw,  C. 

The  wire  by  which  the  figure  is  suspended,  should 
have  plenty  of  spring  to  it.  The  figure  may  be  sus- 
pended by  a  spiral  wire  spring,  or  even  by  an  India 
rubber  spring.  In  the  latter  case,  if  the  figure  is  to 
make  and  break  the  circuit,  by  its  feet,  one  or  two 
wire  conductors  must  be  used  independently  of  the 
rubber  springs. 

Two  or  three  Leclanche  cells  will  work  the  figure 
for  a  short  time — for  larger  periods  a  more  constant 
type  of  generator  must  be  used. 

The  Magic  Drum. 

The  magic  drum  has  been  exhibited  by  many  pro- 
fessional magicians.  When  it  is  shown  on  a  stage,  far 
from  the  eyes  of  the  audience,  it  can  be  easily  manipu- 
lated, with  little  refinement,  as  far  as  concealment  of 
its  mode  of  action  is  concerned.  The  trick  is  doubt- 
less familiar  to  our  readers.  A  drum  is  hung,  by  one 
or  two  cords,  from  the  top  of  the  proscenium  arch,  or 
ceiling,  and,  in  response  to  the  performer's  orders, 
plays,  raps,  etc. 

The  newer  construction  here  illustrated,  due  to 
Mr.  Geo.  M.  Hopkins,  is  superior,  as  it  requires  only 


THE  MAGIC  DRUM. 


one  suspending  cord,  and,  without  close  inspection, 
it  is  far  from  obvious  how  the  result  is  brought  about. 
The  drum  must  contain  some  apparatus  for  mak- 
ing a  sound.  As  shown  in  No.  2,  the  apparatus  con- 
sists of  a  magnet  and  armature,  D,  both  secured  firmly 


FIG.  30.    THE  MAGIC  DRUM. 

to  the  body  of  the  drum.  The  armature  should  be 
as  close  to  the  poles  of  the  magnet  as  possible,  with- 
out touching,  even  when  the  current  is  turned  on. 

A  sudden  exciting  or  releasing  from  excitement  of 
the  magnet  will  produce  a  sound,  on  the  general 
principle  of  the  make  and  break  sounds  in  a  tele- 
phone. 


V8  ELECTRIC  TOT  MAKING. 

The  advantage  of  this  apparatus  is  that  it  can  be 
so  small  and  light  as  to  be  impossible  of  detection  by 
the  closest  inspection.  Placed  close  to  the  embou- 
chure of  the  drum  it  will  fall  outside  of  the  line  of 
sight  of  any  one  looking  into  the  interior. 

If  preferred,  any  form  of  rapping  device,  such  as 
described  for  bells,  can  be  used.  These  will  be  more 
easily  detected. 

From  the  magnet  the  two  terminal  wires  run  to 
opposite  ends  of  the  drum,  and  are  provided  with  two 
ostensible  suspending  cords,  A  B,  as  shown  in  No.  1. 
These  are,  of  course,  really  the  conductors,  and  end 
in  metallic  hooks.  They  are  hooked  into  a  ring,  C, 
which  is  hooked  on  the  end  of  the  suspending  cord. 

The  ring  is  shown  in  detail  in  No.  3.  It  is  of 
ebonite,  or  other  non-conductor,  and  has  two  metallic 
strips,  indicated  by  the  unshaded  areas,  a  b,  within  its 
interior.  The  main  suspending  cord,  which  includes 
two  wires  concealed  in  it,  and  insulated,  one  from  the 
other,  terminates  in  a  hook,  also  of  two  insulated 
pieces  of  metal,  whose  section  is  seen  at  E.  Each 
piece  of  this  hook  is  connected  with  one  of  the  two 
wires  in  the  suspending  cord. 

It  is  obvious  that,  if  the   drum  is  suspended  as  J 
shown,  the  two  wires  of  the  suspending  cord  may,  at 
their  further  end,  be  attached  to  an  electric  circuit. 
If  the  current  is  turned  on  and  off,  a  sound  will  be 
produced  each  time. 

The  single  suspension  cord,  and   the  single  hook 


THE  ELECTRIC  HAMMER.  79 

thereon,  with  the  intermediate  ring,  and  apparent 
absence  of  any  sounding  apparatus  within  the  interior 
of  the  drum,  enhance  the  mystery  above  the  ordinary. 
The  drum  may  even  be  passed  around  for  inspec- 
tion. If  this  is  to  be  done,  it  is  well  to  remove  the 
short  suspending  ends,  A  B,  so  that  only  a  couple  of 
rings  for  hanging  it  will  be  visible.  In  such  case,  the 
cords,  A,  B,  should  have  hooks  at  both  ends. 

The  Electric  Hammer. 

This  toy,  although,  if  made  small,  it  is  only  a  sort 
of  model  of  a  steam  hammer,  can  be  made  quite 
powerful  enough  to  be  of  some  service.  For  the 
latter  end,  it  would  be  well  to  vary  the  construction 
a  little,  and  to  use  a  polarized  hammer  spindle. 
Simplicity  is  favored  by  the  construction  described. 

As  shown  in  the  cut,  it  comprises  a  solenoid  or  deep 
magnetizing  coil,  mounted  on  a  suitable  frame  and 
base.  Under  the  axis  of  the  core  is  placed  an  anvil. 

A  bar  of  soft  iron  nearly  fits  the  opening  in  the 
centre  of  the  coil.  The  lower  end  of  the  bar  is  fitted 
with  an  enlargement  to  represent  the  hammer  head. 

One  battery  wire  connects  directly  with  one  of  the 
coil  terminals.  The  other  battery  wire  is  attached  to 
a  flat  rubbing  plate  of  ebonite,  or  hard  wood,  which 
is  secured  by  a  single  screw  to  the  frame,  so  that  it 
can  be  swung  up  or  down,  as  desired.  The  attach- 
ment of  the  wire  thereto  is  effected  by  a  screw  screwed 
into  the  plate,  and  through  which  its  point  extends. 


80 


ELECTRIC  TOY  MAKING. 


The  point  is  then  filed  off  so  as  to  be  exactly  flush 
with  the  face  of  the  plate. 


Fie.  31.    THE  ELECTRIC  HAMMER.    ELEVATION. 


THE  ELECTRIC  HAMMER. 


81 


The  second  terminal  of  the  coil  is  soldered  to  the 
metallic  frame  at  any  convenient  point. 


FIG.  32.    PLAN  OF  CONNECTIONS  op  ELECTRIC  HAMMER. 

To  the  frame  a  swinging  arm  is  pivoted,  the  same 
pivot  serving  for  it  and  for  the  contact  plate.  It  is 
bent  so  as  to  pass  back  of  the  stem  of  the  hammer, 
and  has  two  striking  pins  extending  from  it.  A  pin 
attached  to  the  hammer  stem,  strikes  one  of  these 
pieces,  as  the  hammer  rises,  and  another  as  it  falls. 

The  action  of  the  hammer,  when  connected  to  a 
battery,  is  as  follows  :  The  current  passes  by  the 
contact  screw,  vibrating  or  swinging  arm,  and  frame 
to  the  magnet,  and  leaves  it  by  the  regular  connec- 
tion. 

The  solenoid  attracts  and  draws  up  the  hammer. 
As  it  rises,  the  striking  pin  encounters  the  upper  pro- 
jection on  the  swinging  arm,  and  raising  it,  displaces 
its  end  from  the  contact  pin.  This  opens  the  circuit, 
stops  the  current,  and  the  hammer  falls.  As  it  nearly 
reaches  the  anvil  the  pin  again  strikes  the  lower  pro- 
jection on  the  swinging  arm,  and,  pressing  it  down, 
brings  its  end  over  the  contact  screw,  thus  closing  the 


82  ELECTRIC  TOT  MAKING. 

circuit  and  again  exciting  the  solenoid.  The  ham- 
mer is  lifted  and  the  same  succession  of  movements 
occurs  over  and  over  again,  with  considerable  rapidity. 
The  contact  or  rubbing  plate  may  be  adjusted  by 
moving  up  or  down,  in  order  to  regulate  the  motion 
of  the  hammer.  As  the  latter  falls  by  gravity  only, 
its  blows  are  not  very  heavy. 

Electric  Insects. 

The  base  of  the  interesting  toy  next  described,  and 
due  to  Mr.  Geo.  M.  Hopkins,  is  an  electro- magnet, 
which  is  made  to  constitute  the  body  of  an  insect. 
The  first  insect  to  be  spoken  of  is  the  electric  butter- 

%. 

The  sectional  views  of  the  body  show  a  straight, 
soft  iron  core,  to  which  an  arched  pole  piece,  h,  is 
attached  at  the  front  of  the  insect's  thorax.  The 
back  of  the  butterfly  is  a  thin  plate  of  iron  attached 
to  the  other  end  of  the  core  by  the  screw,  g.  To  this 
plate  two  small  armatures,  i  i,  are  pivoted  at  /,  as 
shown,  which  extend  down  and  over  the  ends  of  the  pole 
piece,  li.  To  these  armatures  the  wings  are  attached. 
In  making  these  there  is  room  for  artistic  taste. 

The  armatures  are  made  so  much  heavier  than  th(-[ 
wings  th;it  the  latter  stand  erect.  It  is,  however,  a 
simple  matter  to  introduce  a  fine  German  silver  or 
brass  wire  spring  to  keep  the  armatures  away  from 
the  pole  piece. 

The  core  is  wrapped  with  No.  24  silk-covered  wire, 


ELECTRIC  INSECTS. 


83 


and  the  terminals  are  made  to  represent,  or  are  carried 
through  or  back  of  two  of  the  insect's  legs.     The  con- 


FIG.  33.    ELECTRICAL  BUTTERFLY. 

structor  must  not  forget  to  put  on  the  head  with 
proper  adjuncts. 

When  a  current  is  passed  through  the  insect  the 
wings  Avill  be  depressed.  They  will  rise  again  on  being 
released.  The  current  may  be  turned  on  by  hand, 
or  an  automatic  circuit  breaker,  such  as  shown  in 
the  next  cut,  may  be  used. 


ELECTRIC  TOT  MAKING. 


This  consists  of  a  pendulum,  whose  motion  is 
maintained  by  electricity.  Near  its  top  the  rod 
carries  an  armature.  The  lower  end 
of  the  rod,  which  must  be  of  metal, 
and  should  terminate  in  a  platinum 
point,  passes,  in  its  motion,  through 
a  globule  of  mercury.  An  electro- 
magnet is  fixed  near  the  armature. 
The  circuit,  which  includes  the  but- 
terfly, or  several  of  its  kindred,  and 
a  battery,  n,  runs  tli rough  the  cur- 
rent breaker,  thus  : 

One  terminal  goes  to  the  electro- 
magnet,  k,  and  thence  connects  by 
its  suspension  bracket,  with  the  pen- 
dulum rod  ;  going  through  this,  the 
current  passes  through  the  globule 

Fio.  34.    PENDULUM 

CIRCUIT   BREAKER,   of  mercury  on  m,  to  the  other  ter- 
minal which  is  connected  therewith. 

Thus  the  butterfly  and  the  pendulum  magnet  are 
both  excited,  and  the  pendulum  is  attracted.  If  the 
pendulum  is  started  swinging,  it  will,  as  it  leaves 
the  mercury  globule,  open  the  circuit,  and  the  butter- 
fly will  move  its  wings  ;  at  the  same  time  the  magnet 
ceases  to  pull  it.  It  swings  back,  and  as  it  passes 
through  the  globule,  is  attracted  by  the  magnet  as 
the  circuit  closes,  and  the  butterfly  again  moves  its 
wings  in  the  reverse  direction. 

This  can  be  kept  up  as  long  as  desired.     The  exact 


ELECTRIC  INSECTS.  86 

position  of  the  mercury  globule,  to  give  ti  good  swing, 
must  be  determined  by  experiment.     The  plumb-bob 


FIG.  35.    ELECTRICAL  DRAGON-FLY  AND  BEE. 

is  also  made  adjustable,  so  as  to  allow  of  varying  the 
time  of  movement  of  the  insect's  wings. 

The   dragon-fly  and  bee  are    more  independent. 
They  are  by  nature  quicker  in  their  motions  than 


86  ELECTRIC  TOT  MAKING. 

the  butterfly,  and  are  constructed  to  rapidly  move  or 
"buzz"  their  wings. 

The  core  is  bent  at  right  angles  at  the  head  as 
shown  in  the  section  of  the  dragon-fly.  The  arma- 
ture, J,  of  soft  iron,  is  carried  by  a  spring  fastened 
at  c  to  the  core  of  the  magnet.  This  is  wound  also 
with  No.  24  silk-covered  wire.  One  terminal  is 
connected  to  the  spring  at  c.  From  the  armature  an 
extension  of  the  spring  reaches  down  over  the  insect's 
front,  and  is  bent  to  receive  a  contact  screw,  d,  best 
tipped  with  platinum.  A  contact  piece,  e,  connects 
with  a  wire  running  through,  or  by,  one  of  the  legs. 
The  other  terminal  of  the  magnet  wire  runs  by 
another  leg.  Thence  the  two  are  carried  to  a  battery. 

The  whole  arrangement,  it  will  be  seen,  is  an 
automatic  circuit  breaker,  and  as  long  as  the  current 
;s  turned  on,  will  keep  the  armature  in  vibration. 

Properly  shaped  wings  made  of  mica,  and  painted 
to  represent  the  veins,  are  attached  in  any  desired 
position  to  the  armature.  The  current  causes  these 
to  rapidly  vibrate. 

A  very  nice  way  to  mount  the  insects  is  to  place 
them  on  some  artificial  flowers  in  a  flower  pot,  which 
latter  contains  a  Leclanche  battery. 

One  of  the  battery  terminals  connects  with  the 
insect.  The  other  runs  to  the  base  of  the  flower  pot. 
Here  it  nearly  meets  one  of  the  terminal  wires  from 
the  insect.  A  globule  of  mercury  is  so  disposed  as  to 
leave  the  circuit  open,  if  all  is  on  a  level  table.  If 


THE  INCANDESCENT  LAMP.  87 

lifted,  or  tipped  a  little,  the  mercury  shifts  and 
makes  contact  with  both  wires,  closing  the  circuit 
and  making  the  insects  start  into  seeming  life. 

The  Incandescent  Lamp. 

The  amateur  should  not  attempt  to  make  incandes- 
cent carbon  filament  lamps.  These  are  for  sale,  of  all 
descriptions  and  sizes.  A  platinum  wire  lamp,  un- 
regulated, is  easily  made,  and  with  a  carefully  regu- 
lated current  is  very  good  as  a  toy,  but  is  of  little 
practical  value.  The  end  of  a  test  tube  may  be  used 
to  represent  the  bulb,  and  a  bent  loop  of  fine  platinum 
wire  to  represent  the  filament.  The  ends  of  the  plati- 
num are  soldered  to  two  copper  wires  considerably 
thicker  than  themselves.  The  copper  wires  are 
thrust  through  a  cork  which  closes  the  end  of  the  tube. 

The  platinum  wire  should  be  fine,  No.  28  to  30. 
The  copper  wire  should  be  not  less  than  No.  25. 

The  next  cut  shows  a  regulated  platinum  lamp, 
which  might  render  real  service,  although  it  would 
never  be  as  efficient  as  the  carbon  filament  lamp,  with 
its  almost  perfect  vacuum. 

A  base  carries  two  binding  posts  and  a  glass 
shade  or  bulb,  and  the  mechanism  of  the  lamp. 
From  the  binding  posts  wires  run  to  a  post,  B,  and  a 
short  screw  at  C.  The  latter  screw  holds  down 
against  the  base  a  high  arched  piece.  To  the  post,  B, 
a  rocker,  A,  is  pivoted.  From  the  arched  piece  to 
the  rocker  a  platinum  wire,  P,  extends. 


88  ELECTRIC  TOT  MAKING. 

As  shown  in  the  cut,  the  current  entering  by  one 
post  passes  through  the  wire  and  out  by  the  other 
post.  As  the  wire  expands  with  the  heat,  the  left 
end  of  the  rocker  descends.  The  adjustment  is  such 
that  contact  is  made  before  the  platinum  is  hot  enough 


FIG.  36.    SKLF-REGULATING  PLATINUM  LAMP. 

to  melt.  This  short  circuits  the  wire,  and  the  heat 
falls ;  as  the  wire  contracts,  it  breaks  the  contact  and 
again  grows  hot.  These  operations  in  practise  suc- 
ceed each  other  so  rapidij  and  are  of  such  slight 
degree,  that  all  appears  perfectly  stationary,  and  no 
vibration  is  perceptible. 


CHAPTER  VII. 

SPARK  AND  INDUCTION  COILS,  AND  ALLIED 
SUBJECTS. 

THE  SPARK  COIL — THE  INDUCTION  -COIL — RECORD- 
OX'S  INDUCTION  COIL — THE  MAGNETO-GENERA- 
TOR—  ELECTRIC  ARTILLERY  —  ELECTRIC  GYM- 
NASTICS— ANO-KATO — SIMPLE  EXPERIMENTS  IN 

STATIC    ELECTRICITY. 

The  Spark  Coil. 

FOR  the  production  of  a  simple  spark  for  lighting 
gas,  firing  an  explosive  mixture,  and  the  like,  a  spark 
coil  may  be  employed.  It  is  simpler  in  construction 
than  an  induction  coil.  It  practically  represents  a 
single  coil,  either  primary  or  secondary,  of  the  more 
complicated  apparatus. 

To  construct  one,  a  core  of  iron  wire  is  first  made. 
This  may  be  a  bundle  of  pieces  of  wire  of  gauge  No.  20, 
or  thereabouts.  The  pieces  composing  it  should  be 
about  eight  inches  long,  and  the  bundle  should  repre- 
sent a  cylinder  about  f  inch  in  diameter. 

A  very  good  plan  is  to  put  the  pieces  of  wire  in  a 
coal  fire  in  the  evening,  and  to  allow  them  to  become 


90  ELECTRIC  TOT  MAKING. 

red  hot.  They  are  left  in  the  fire  over  night  until 
it  has  grown  cold.  This  anneals  them  and  leaves 
them  covered  with  a  thin  film  of  oxide.  The  latter  is 
a  non-conductor  of  electricity,  and  its  presence  acts  to 
break  up  the  continuity  of  the  core. 

On  this  the  coil  is  wound.  It  may  be  made  of  No. 
20  wire,  insulated  with  cotton.  What  is  sold  as 
magnet  wire  will  answer  perfectly.  This  should  be 
wound  on  until  the  whole  is  about  three  times  the 
diameter  of  the  core.  The  wire  windings  should  cover 
as  nearly  as  possible  the  whole  of  the  core. 
•  If  such  a  coil  is  placed  in  circuit  with  a  battery, 
the  parallel  component  windings  of  wire  act  one  upon 
the  other,  when  the  current  is  turned  on  or  off,  and 
produce  a  high  potential  difference.  This  causes  the 
production  of  a  spark.  The  spark  is  strongest  when 
the  current  is  suddenly  shut  off  by  breaking  the  cir- 
cuit. As  the  coil  is  normally  on  an  open  circuit,  and 
as  the  operation  of  producing  a  spark  consists  in 
suddenly  depressing  and  releasing  a  key,  thus  open- 
ing and  closing  the  circuit  in  quick  succession,  a 
double  spark  or  discharge  is  produced. 

The  battery  for  operating  a  spark  coil  should  be,  as 
a  general  rule,  arranged  in  series.  This  gives  as  a 
starting  point  the  highest  attainable  potential  differ- 
ence, which  again  is  magnified  or  increased  by  the 
self-induction  of  the  coil. 

The  tendency  of  the  day  is  to  use  coils  for  high 
tension  effects.  Regular  induction  coils  are  to  be 


THE  IND  UCTION  COIL.  9 1 

recommended  for  powerful  tension,  but  where  a  spark 
suffices,  the  spark-coil  answers  every  purpose. 

So  true  is  this  that,  on  an  emergency,  any  electro- 
magnet, such  as  is  used  in  a  telegraph  sounder,  or 
for  lifting  weights,  and  the  like,  can  be  made  to  do 
service  as  a  spark-coil.  The  ready  production  of  a 
spark  on  opening  a  circuit  goes  to  prove  that  it  in- 
cludes a  high  potential  battery,  or  that  electro- 
magnets, or  some  form  of  coil,  are  actuated  by  it. 

The  Induction  Coil. 

The  induction  coil  is,  in  general  terms,  an  apparatus 
for  converting  a  current  of  one  intensity  into  a  current 
of  a  greater  or  less  intensity.  Conversely  with  the 
change  of  intensity  there  is  an  inverse  change  in  the 
potential  difference  of  such  parts  of  the  circuit  as 
represent  the  entering  and  outgoing  terminals  of 
the  coil.  To  bring  about  this  change  a  steady  cur- 
rent cannot  be  directly  used — if  such  is  the  one  to  be 
acted  upon  it  must  first  be  converted  into  an  irregular 
or  varying  one.  The  first,  or  unconverted  current,  is 
called  the  primary  current.  The  converted  current, 
produced  by  the  action  of  the  coil,  is  called  the 
secondary  current ;  it  is  always  an  interrupted  cur- 
rent, and  of  the  type  known  as  alternating. 

An  induction  coil  may  be  very  easily  constructed. 
As  a  toy,  for  giving  shocks  and  similar  uses,  it  may 
be  quite  small.  But  as  the  size  increases  the  difficul- 
ties of  construction  increase.  The  very  large  coils, 


92  ELECTRIC  TOT  MAKING. 

giving  from  twelve  to  forty-two  inch  sparks,  require 
the  highest  skill  of  the  apparatus  maker. 

For  the  amateur  the  induction  coil  will  generally 
be  designed  to  increase  potential  difference  at  the 
expense  of  intensity.  The  illustrations  show  the 
features  of  construction  of  a  simple  coil  designed  to 
do  this. 

Before  going  further  it  should  be  understood  that 
nothing  absolute  can  be  said  of  the  size  of  a  coil,  or 
of  the  wire  composing  it.  All  this  is  a  matter  of 
calculation,  and  depends  upon  the  current  to  be  used, 
and  upon  the  current  to  be  obtained  from  the  coil. 

The  coil  proper  of  the  drawing  consists  of  the 
core,  A,  primary  coil,  B,  insulating  coating,  C,  and 
secondary  coil,  D.  The  wires  of  the  secondary  coil 
are  kept  insulated  from  the  primary,  and  the  greatest 
care  must  also  be  taken  to  keep  the  different  wind- 
ings of  both  secondary  and  primary  insulated  from 
each  other. 

The  core  consists  of  a  bundle  of  iron  wires,  about 
No.  18.  These  are  laid  together  so  as  to  form  a  cylin- 
der. They  may  be  annealed  and  oxidized  as  described 
for  the  spark  coil.  After  wrapping  the  core  with 
some  shellacked  paper,  the  primary  wire  is  wound  on 
as  compactly  as  possible.  It  should  be  insulated  wire, 
and  it  is  well,  if  it  is  cotton  covered,  to  paint  over 
the  successive  layers  with  alcoholic  solution  of  shellac. 

For  ordinary  coils  No.  18  wire  is  a  good  size,  and 
two  wrappings  around  the  core  may  be  employed. 


THE  INDUCTION  COIL.  93 

A  paste-board  tube  such  as  used  for  mailing  draw- 
ings or  papers  which  are  not  to  be  folded,  serves  to 


FIG.  37.    INDUCTION  COIL. 

cover  the  primary  coil  a-ud  core.  On  this  the  second- 
ary core  is  wound.  The  tube  must  be  well  paraf- 
fined. 

Here,  far  more  precautions  in  the  way  of  insulating 
the  wire  have  to  be  taken.  The  wire  itself  is  much 
finer.  If  the  potential  is  to  be  raised  to  one  thousand 
times  the  original  diffeience,  the  wire  will  answer  if 
of  one-thousandth  the  section  of  the  primary.  Turns 
enough  must  then  be  given  to  it  to  ensure  this  ratio. 

As  a  matter  of  practise  the  secondary  is  often  made 
of  coarser  wire  than  is  required  under  the  above  sup- 


94  ELECTRIC  TOT  MAKING. 

position.  Very  fine  wire  is  expensive,  and  is  difficult 
10  work,  as  it  is  liable  to  break  very  easily  when  being 
wound.  No.  36  wire  is  fine  enough  for  all  ordinary 
purposes. 

Either  bare,  or  insulated,  or  covered  wire  may  be 
used.  In  any  case  the  number  of  turns  it  takes 
around  the  core  and  primary  must  be  equal  to  the 
turns  of  the  primary  multiplied  by  the  factor  express- 
ing the  desired  ratio  of  increase  of  potential  diffrr- 
ence. 

Suppose  a  coil  is  to  produce  one  thousand  times  as 
great  voltage  as  that  existing  between  the  primary 
terminals,  and  that  the  primary  has  fifty  turns.  Then 
the  secondary  must  have  fifty  thousand  turns. 

If  bare  wire  is  used  a  layer  is  wound  upon  the  in- 
sulating tube,  C,  the  successive  turns  lying  as  close  as 
possible  without  touching.  Then  a  piece  of  paper  is 
wound  over  the  wire,  and  is  shellacked,  and  the  wind- 
ing is  continued  over  it.  This  goes  on  until  the 
desired  number  of  turns  are  obtained.  As  this  in- 
volves a  long  piece  of  winding  it  is  best  to  do  it  on 
the  lathe. 

An  excellent  plan  is  to  wind  only  a  half  inch  in 
length  of  the  secondary  at  a  time,  but  to  wind  each 
half  inch  to  the  full  thickness  before  beginning  the 
next.  To  execute  this,  a  bit  of  thin  board  with  a 
hole  the  size  of  the  insulating  tube  in  it  is  needed. 
This  is  thrust  up  to  within  half  an  inch  of  the  end 
of  the  coil,  and  the  space  between  it  and  the  end  is 


THE  INDUCTION  COIL. 


95 


wound  to  the  full  thickness ;  then  it  is  shifted  half 
an  inch  and  the  winding  is  thus  continued  until  done. 
In  any  case  a  temporary  flange  of  some  kind  is 
needed  at  the  ends  to  keep  the  coils  square. 


Fia.  38.    END  PIECE  OF  FRAME  OF  INDUCTION  COIL. 

From  time  to  time  the  wire  should  be  tested  for 
continuity,  as  it  is  very  apt  to  break.  If  it  does  part, 
it  may  be  carefully  twisted  together,  and  it  is  well  to 
solder  it.  This  can  be  done  in  the  flame  of  an  alco- 
hol lamp.  In  testing  its  continuity  an  ordinary 
compass  can  be  utilized  as  the  galvanometer.  If  a 
dozen  turns  of  the  wire  are  taken  around  it  a  slight 
current  will  deflect  the  needle.  The  compass  must 


96  ELECTRIC  TO  T  MAKING. 

be  so  placed  that  the  coils  lie  in  the  magnetic  merid- 
ian. As  battery,  a  copper  coin  and  a  bit  of  galvan- 
ized iron,  immersed  for  the  moment  in  dilute  sul- 
phuric acid,  will  answer  if  the  galvanometer  is  sensi- 
tive enough.  It  is  sufficient  to  discern  the  smallest 
possible  change  of  direction  of  the  compass-needle. 

If  insulated  wire  is  used,  it  should  be  shellacked 
from  time  to  time  as  wound,  and  the  paper  between 
the  layers  should  always  be  used  as  described. 

When  all  is  wound  it  is  mounted  in  a  frame  as 
shown,  the  coil  being  carried  by  two  end  pieces,  H, 
H,  one  of  which  is  shown  in  side  elevation  on  a  larger 
scale  than  that  of  the  illustration  of  the  coil. 

The  terminals  of  the  secondary  lead  to  and  are 
soldered  to  two  binding  posts,  E,  E.  The  terminals 
of  the  primary,  K,  K,  connect  with  a  source  of  cur- 
rent which  must  be  very  variable,  intermittent,  or 
alternating. 

If  to  the  secondary  terminals,  or  binding  posts,  a 
couple  of  pieces  of  wire  are  attached,  the  ends  of 
which  are  held  in  the  hands,  and  if  then  an  inter- 
mittent current  is  passed  through  the  primary,  a 
series  of  shocks  will  be  experienced. 

For  this  purpose  it  is  best  to  attach  handles  of 
brass  tubing,  about  half  an  inch  in  diameter,  to  the 
ends  of  the  wires,  in  order  to  give  a  larger  surface  of 
contact.  Wet  sponges  may,  with  advantage,  be  used 
on  the  tubing,  although  as  this  is  not  necessary  and 
is  rather  unpleasant,  it  is  not  generally  done. 


THE  IND  UCTION  COIL.  97 

Sparks  may  also  be  taken  from  the  coil  by  bringing 
the  ends  of  two  conductors  from  the  secondary  ter- 
minals sufficiently  close.  A  very  small  coil,  two  or 
three  inches  long,  will  give  a  one- eighth  inch  spark, 
and  some  of  the  large  ones  will  give  a  spark  several 
feet  long,  one  which  will  pierce  a  glass  plate  two 
inches  or  more  in  thickness. 

The  primary  circuit  may  be  broken  by  hand.  One 
of  the  old  methods  consisted  in  connecting  one  end 
of  the  primary  to  the  battery,  and  the  other  to  a  very 


FIG.  39.    CIRCUIT  BREAKER. 

coarse  cut  file.  The  teeth  of  the  file  might  be  an 
eighth  of  an  inch  apart,  and  as  high  as  possible. 
Then  the  other  wire  from  the  battery  was  drawn 


98  ELEGTR1G  TOY  MAKING. 

across  the  file,  and,  as  it  jumped  from  tooth  to  tooth, 
effected  the  desired  "make  and  break." 

Another  way  of  doing  it  by  hand  is  shown  in  the 
cut.  A  cog-wheel  from  an  old  clock,  or  elsewhere,  is 
mounted  on  a  metallic  frame,  which  is  in  connection 
with  one  of  the  battery  wires.  A  spring  wire  presses 
against  the  teeth  as  the  wheel  rotates.  This  spring 
is  in  connection  with  one  of  the  primary  terminals  of 
the  coil.  The  other  primary  terminal  is  in  direct 
connection  with  the  battery.  Thus  the  make  and 
break  is  obtained  by  turning  the  wheel. 

The  coil  itself  may  be  made  to  do  the  making  and 
breaking.  As  shown  in  the  cut  it  is  thus  arranged  : 
On  the  base  are  two  binding  posts,  which  are  the 
primary  terminals.  One  of  the  primary  terminal 
wires,  K,  K,  runs  directly  to  one  of  the  binding  posts. 
The  other  primary  terminal  wire  runs  to  the  base  of 
the  vertical  spring,  F.  At  its  top  this  spring  carries 
a  block  of  soft  iron  which  acts  as  an  armature.  The 
other  binding  post  seen  in  the  elevation  connects 
with  the  metallic  standard,  G.  An  adjustable  con- 
tact screw,  with  platinum  point,  goes  through  the  top 
of  the  standard.  The  spring  normally  presses  against 
this  screw.  It  is  well  to  rivet  a  little  bit  of  platinum 
on  the  spring  at  the  point  of  contact. 

When  the  terminals  from  a  battery  are  attached  to 
the  binding  screws  the  action  is  obvious.  The  spring, 
F,  making  contact  through  G  with  the  battery,  closes 
the  primary  circuit  and  a  current  goes  through  the 


THE  INDUCTION  COIL.  9i> 

primary.  This  magnetizes  the  core  and  the  armature 
on  the  spring  is  attracted.  It  draws  the  spring  away 
from  the  contact  screw  and  breaks  the  circuit.  The 
core  ceases  to  be  magnetic  and  the  spring  flies  back 
and  renews  the  contact.  This  action  is  kept  up  as 
long  as  connection  with  the  battery  is  maintained, 
the  makes  and  breaks  succeeding  each  other  with 
great  rapidity. 

As  thus  described,  the  induction  coil  is  far  from 
perfect.  A  violent  sparking  action  takes  place  at  the 
make  and  break  contact  and  there  is  considerable 
waste  of  energy.  Both  these  bad  features  can  be 
diminished  by  the  use  of  a  condenser,  whose  construc- 
tion will  be  next  explained. 

It  would  consist,  in  its  simplest  plan,  of  two  leaves 
of  tin-foil  separated  from  each  other,  one  connected 
to  the  spring,  F,  and  the  other  to  the  standard,  G. 
The  area  must  be  quite  large  so  that  as  a  matter  of 
convenience  it  is  best  built  up  of  small  pieces  of  tin- 
foil laid  in  a  pile  that  fits  the  base  of  the  instrument, 
which  is  made  into  a  box  to  contain  them.  The  con- 
nections and  general  features  of  the  condenser  are 
best  shown  in  the  plan  view. 

Each  piece  of  foil  is  cut  with  projecting  ears,  A,  B, 
at  one  of  the  corners.  The  shape  is  seen  in  the  plan 
view  given  here.  A  piece  of  paper,  saturated  with 
paraffine  wax,  is  placed  between  each  two  sheets.  In 
piling  up  the  sheets  of  tin-foil  the  ears,  A,  or  B,  of 
each  sheet  are  placed  at  the  opposite  corners  as 


100 


ELECTRIC  TOT  MAKING. 


indicated  in  the  plan.  It  is  now  evident  that  if  the 
projecting  ears  are  bent  down  or  pressed  together, 
each  set  of  leaves  of  tin-foil  will  be  insulated 
from  the  other,  but  all  the  leaves  of  each  set  will 
be  in  electrical  connection  with  each  other.  To 


FIG.  40.    PLAN  VIEW  OF  INDUCTION  COIL. 

ensure  all  this,  the  paper  should  be  cut  an  eighth  of 
an  inch  longer  and  wider  than  the  tin-foil.  The 
paper  can  be  easily  waxed  or  paraffined  by  applying 
the  wax  in  shavings  and  melting  it  with  a  hot  sad- 
iron, or  in  an  oven  or  over  a  stove. 

Referring  now  to  the  plan,  in  it  E  denotes  one  of 
the  binding  posts  to  which  the  battery  wire  is  to  be 
connected.  H  is  the  primary  coil.  From  E  a  wire  is 
carried  to  and  connects  at  D  with  one  of  the  termi- 
nals of  H.  The  other  terminal  of  H,  denoted  by  C, 
connects  with  the  spring  (F,  in  the  elevation),  whose 
base  is  shown  in  the  plan.  The  other  binding  post 
which,  it  will  be  remembered,  is  in  connection  with  the 


THE  INDUCTION    COIL.  101 

contact  screw  post  (G,  of  the  elevation),  is  shown  at  F 
in  the  plan.  From  this  contact  screw  post  a  wire 
connects  with  one  set  of  tin-foil  sheets,  A,  while  from 
the  spring  u  wire  connects  with  the  other  set  of 
sheets,  B. 

The  action  of  the  condenser  is  apparent  in  the 
reduction  of  the  size  of  the  spark  between  the  make 
and  break  surfaces,  and  in  the  lengthening  of  the 
other  secondary  spark.  In  other  words,  a  condenser 
greatly  improves  the  action  of  an  induction  coil,  and 
should  always  be  used. 

As  an  example  of  a  miniature  coil  the  following 
data  may  be  given  :  Core,  4  inches  long,  and  as 
thick  as  a  lead  pencil.  Length  between  end  pieces,  3 
inches.  Primary  coil,  two  ounces  of  No.  18  wire. 
The  secondary  wound  to  within  %  inch  of  the  insu- 
lating tube,  with  two  ounces  of  No.  36  wire.  The  con- 
denser, twenty  pieces  tin-foil,  each  3  inches  square. 

An  excellent  way  of  making  the  insulating  tube  is 
to  saturate  a  piece  of  blotting  paper  with  paraffine 
wax.  A  wooden  mandrel  is  wrapped  with  a  piece  of 
writing  paper,  whose  free  end  is  pasted  down  to  the 
paper.  This  must  be  free  to  slide  on  and  off.  The 
mandrel  must  be  of  the  diameter  of  the  primary.  On 
this  the  blotting  paper  is  wound,  being  pressed  into 
place  with  a  hot  iron.  This  solidifies  it  by  melting 
the  wax.  It  should  be  one-twentieth  of  an  inch 
thick. 

The  tension  of   the  shocks  may  be  graduated  by 


102 


ELECTRIC  TOY  MAKING. 


Bulling  the  core  out  or  pressing  it  in.  Its  removal 
greatly  reduces  the  intensity  of  action.  Or  else  a 
space  may  be  left  between  the  secondary  and  pri- 
mary, and  a  brass  tube  may  be  arranged  to  slide  in 
and  out  of  this  space.  The  removal  of  the  tube 
increases  the  energy  of  action. 

Recor don's  Induction  Coil. 

A  very  good  form  of  induction  coil  is  shown  in  the 
next  cut  which  at  least  possesses  the  merit  of  novelty. 


FIG.  41.    RECOUDON'S  INDUCTION  COIL. 


It  is  disadvantageous  in  not  admitting  the  convenient 
use  of  a  wire  core. 

The  core  which  is  hollow,  is  made  of  soft,  annealed 


RECORDON'S  INDUCTION  COIL.  103 

iron,  turned  so  as  to  represent  a  spool  or  bobbin  with 
deep  flanges  at  eacli  end.  It  is  mounted  as  shown, 
wound  with  primary  and  secondary  coil,  B,  as  de- 
scribed for  the  other  form  of  coil.  The  secondary  con- 
nects with  two  binding  posts  on  the  base,  one  of  which 
is  seen  at  N.  Of  the  primary  terminals,  one  connects 
with  the  standard,  D,  the  other  with  the  binding 
post,  b.  From  the  binding  post,  51,  a  wire  runs  to  the 
standard,  C. 

To  the  top  of  the  standard,  D,  a  spring  is  screwed 
to  which  an  iron  block,  A,  is  attached.  The  stand- 
ard, C,  carries  a  contact  screw  with  platinum  point. 
The  iron  block,  A,  acts  as  the  armature  of  the  mag- 
net. The  piece,  P,  is  simply  designed  to  regulate 
the  period  of  vibration  and  prevent  too  rapid  a 
succession  of  makes  and  breaks.  The  battery  con- 
nects with  the  binding  posts,  J1  and  b, 

When  the  current  passes  to  the  primary  coil 
through  the  standard,  C,  contact  screw,  spring  and 
standard,  D,  it  excites  the  core,  which  becomes  a 
magnet.  The  armature,  A,  is  attracted  and  draws 
the  spring  away  from  the  contact  screw.  This  opens 
the  circuit.  The  core  ceases  to  attract  the  armature 
and  it  springs  back.  The  contact  screw  again 
comes  in  contact  with  the  spring,  and  the  current 
again  passes.  Thus  the  make  and  break  is  effected 
practically  as  in  the  case  of  the  other  coil. 

Although  shown  without  a  condenser,  it  will  work 
far  better  if  it  has  one. 


104  ELECTRIC  TOT  MAKING. 

This  coil  may  be  fitted  with  a  regulator.  To  do 
this  the  barrel  should  be  turned  down  so  as  to  be  very 
thin.  It  may  even  be  made  of  sheet  iron,  bent  into 
a  tube  and  soldered  along  its  seam,  and  to  the  heavy 
flanges.  A  bundle  of  iron  wires  is  then  arranged  to 
fit  into  the  tube,  and  to  be  slid  in  or  out  as  desired. 
The  more  there  are  within  the  tube  the  greater  will 
be  the  effect  of  the  coil. 

The  dimensions  of  the  coil  illustrated  are  as  fol- 
lows:  Diameter  of  coil,  3Ty7  inches;  thickness  of 
flanges,  T%-  inch  ;  exterior  diameter  of  core,  1TV  inch  ; 
interior  diameter  of  flange,  1^-  inch  ;  distance  be- 
tween flanges,  1^  inch.  Primary  wire,  -^frlb.  avoir- 
dupois No.  18  wire  ;  secondary  wire  (in  31  layers), 
•j^j-  Ib.  avoirdupois  No.  32  wire.  There  is,  of  course, 
nothing  absolute  in  these  dimensions. 

The  Magneto- Generator. 

A  very  powerful  and  compact  form  of  magneto- 
generator  is  the  subject  of  the  next  cut.  As  arranged 
it  is  designed  to  give  rapid  alternating  shocks. 

Two  powerful  horseshoe  magnets  are  mounted  as 
shown.  A  pair  of  bobbins,  such  as  those  used  on  the 
legs  of  horseshoe  electro-magnets,  arc  carried  by  a 
vertical  spindle  so  as  to  rotate  between  the  opposing 
poles.  The  letters,  N  and  S,  seen  on  the  magnet  ends, 
denote  the  north  and  south  poles  respectively.  The 
bobbins  have,  as  cores,  two  bundles  of  iron  wire, 
which  should  be  annealed  and  oxidized.  Each  piece 


THE  MAGNETO-GENERATOR. 


105 


of  wire  should  be  long  enough  to  nearly  reach  from 
face  to  face  of  the  magnets. 

As  wire,  Nos.  30  to  36  may  be  used.  The  bobbins 
may  be  two  inches  long,  and  wound  with  enough 
wire  to  fill  them  up  to  a  diameter  of  one  inch.  Be- 
tween every  layer  of  winding  a  piece  of  paraffined 
paper  must  be  smoothly  wound.  Shellacked  paper 


FIQ.  42.    MAGNBTO-GENKBATOB. 

may  be  used  instead,  and  each  of  the  layers  may  then 
be  varnished  with  alcoholic  solution  of  shellac.  The 
general  precautions  observed  in  winding  the  secondary 
of  an  induction  coil  must  be  followed  here. 

In  laying  on  the  windings  the  greatest  care  must  be 
taken  to  avoid  kinks,  or  sudden  bends.  From  time 
to  time  the  part  wound  should  be  tested  with  a  gal- 
vanometer, as  in  the  case  of  the  induction  coil,  to  see 
if  it  passes  a  current.  If  the  wire  breaks,  the  ends 
must  be  soldered  after  neat  twisting  together. 


106  ELECTRIC  TOT  MAKING. 

The  wire  on  the  bobbins  must  be  wound  in  opposite 
directions,  one  right  and  the  other  left  handed,  ex- 
actly as  in  a  horseshoe  electro-magnet. 

On  the  upper  end  of  the  spindle  are  an  insulated 
collar  and  an  insulated  crown-wheel.  The  bobbins 
are  connected  together  so  as  to  give  the  current  an 
opposite  direction  in  each  one.  The  connecting  wire 
is  made  to  lead  diagonally  from  front  of  one  to  rear 
of  the  other.  This  leaves  two  free  terminals.  One  is 
soldered  to  the  collar,  the  other  to  the  crown-wheel. 

Two  springs  of  copper,  brass,  or  silver,  press,  one 
against  the  collar,  the  other  against  the  teeth  of  the 
crown-wheel.  Multiplying  gear  is  applied  to  drive 
the  mechanism,  by  turning  the  bobbins  rapidly 
around  in  the  magnetic  field  created  by  the  magnets. 

The  springs  are  secured  to  insulated  binding  posts, 
to  each  of  which  flexible  wire,  or  conducting  cord, 
is  connected.  The  other  ends  of  the  pieces  have 
handles. 

If,  now,  the  hand-wheel  is  rapidly  turned,  while  the 
handles  are  held  one  in  each  hand,  or  are  applied  to 
different  parts  of  the  body,  a  succession  of  rapidly 
succeeding  shocks  will  be  felt. 

Should  it  be  desired  to  have  the  impulses  all  run 
in  the  same  direction,  the  commutator  shown  and 
described  on  page  58,  must  be  used,  instead  of  the 
collar  and  crown-wheel. 

A  well  made  magneto-generator,  such  as  described, 
will  give  powerful  shocks.  If  wound  with  coarser 


ELECTRIC  ARTILLERY.  107 

wire,  No.  25,  or  thereabouts,  and  if  provided  with  the 
commutator  just  alluded  to,  it  will  give  quite  cur- 
rent enough  to  heat  fine  platinum  wire  and  decom- 
pose water. 

Electric  Artillery. 

Explosions  of  gunpowder,  or  of  hydrogen,  or  of  coal 
gas,  mixed  with  oxygen  or  air,  can 
be  produced  by  the  electric  spark, 
or  by  an  incandescent  wire.  The 
cut  shows  what  may  be  termed  an 
electric  mortar.  It  may  be  made  of 
metal  or  of  wood.  Two  wires,  in- 

FIG.  43.    ELECTRIC  ,    ,     ,     ..  , ,  ,      .   ,       ,    , , 

MORTAR.  sulated  from  the  material  of  the 

mortar,  if  the  latter  is  of  metal,  are  arranged  as 
shown,  approaching  close  to  each  other,  but  not 
touching  within  the  cavity  of  the  mortar. 

Such  a  mortar  may  be  charged  with  powder,  and  if 
a  spark  from  a  Leyden  jar,  induction  or  spark 
coil,  is  passed  through  it,  the  powder  will  explode.  A 
ball  placed  on  the  mouth,  which  is  countersunk  to 
receive  it,  will  be  shot  into  the  air.  A  magneto- 
generator  may  be  used  to  produce  the  spark. 

The  ignition  by  a  spark  is  not  always  certain.  It  is 
a  common  practice  to  include  in  the  circuit,  if  a 
Leyden  jar  is  employed,  a  piece  of  wet  cord,  which 
makes  the  spark  more  efficient.  The  spark  may  be 
taken  also  directly  from  an  electric  machine. 

It  is  better  to  produce  these  explosions  by  a  wire 
heated  by  a  current.  For  such,  the  simplest  method 


108  ELECTRIC  TOT  MAKING. 

is  to  fit  the  barrel  with  a  plug,  which  screws  tightly 
into  it,  and  through  which  the  two  wires,  well  insu- 
lated, pass  as  shown  in  the  cut. 

The  wires  protrude  a  little  on  the  inner  side,  and 


€1 — 

FIG.  44.    ELECTRIC  OR  VOLTAIC  PISTOL. 

across  from  end  to  end  of  them  a  very  fine  wire,  of 
platinum  or  of  iron,  is  carried.  It  must  be  in  good 
electrical  connection  with  both,  which  is  best  insured 
by  soldering.  The  copper  wires  may  be  No.  20  or 
thereabouts.  What  is  the  simplest,  and  really  the 
best  construction,  is  to  make  a  plug  of  some  non-con- 
ducting material,  such  as  hard  wood,  and  to  thrust 
the  bare  wires  through  holes  which,  if  in  wood,  may 
be  bored  with  a  brad-awl.  The  connecting  wire 
should  be  very  fine  and  the  shorter  it  is  the  hotter  it 
will  get.  If  too  great  a  current  is  employed  the 
wire  will  be  melted.  It  is  well  to  test,  by  experiment, 
how  many  cups  of  the  experimenter's  battery  are  re- 
quired to  heat  it  to  redness. 


ELECTRIC  ARTILLERY.  109 

All  this  is  a  subject  of  calculation,  and  those  who 
wish  can  readily  work  out  the  problem  for  them- 
selves. 

Such  an  apparatus  may  be  called  an  electric 
primer.  A  pinch  of  gunpowder  can  be  ignited  by 
passing  a  current  through  the  wire,  immersed  in  or 
covered  by  it. 

The  voltaic  pistol  simply  consists  of  a  tube  of  brass 
with  a  handle  and  a  side  connection  into  which  the 
plug  screws.  By  holding  it  mouth  downwards  for  a 
second  or  two,  some  inches  above  and  over  an  open 
unlighted  gas-burner,  it  will  be  charged  with  a  mix- 
ture of  air  and  gas.  A  cork  is  now  thrust  into  its 
mouth  ;  it  is  held  pointed  in  the  right  direction,  and 
a  current  is  passed  through  the  cap.  The  mixture  ex- 
plodes and  drives  the  cork  out.  To  produce  a  strong 
explosion,  the  proper  mixture  is  about  six  of  air  to 
one  of  gas.  Such  a  mixture  may  be  made  in  a  test 
tube  or  even  in  a  bottle.  One  sixth  of  its  volume  of 
water  is  introduced  and  the  tube  or  bottle  is  inverted, 
without  loosing  any  water,  into  a  basin  of  water  with 
its  mouth  under  the  surface  ;  the  rest  of  the  bottle 
is  now  filled  by  bubbling  gas  into  it. 

The  pistol  barrel  is  filled  with  water  ;  it  is  inverted 
in  the  basin,  and  the  contents  of  the  bottle  are  intro- 
duced, bubbling  through  the  water.  It  is  removed, 
mouth  downwards,  and  quickly  corked,  and  all  is 
ready  for  the  explosion. 

For  an  extremely  violent  report,  a  mixture  of  one 


110  ELECTRIC  TOT  MAKING. 

volume  of  oxygen  to  two  volumes  of  hydrogen  gas 
may  be  used. 

It  is  obvious  that  many  variations  can  be  intro- 
duced in  this  experiment.  A  bottle  may  take  the 
place  of  the  pistol.  The  wires  may  be  thrust  through 
the  cork,  which  will  take  the  place  of  both  the  cap 
and  cork.  The  bottle  is  best  filled  over  water  to  se- 
cure the  right  mixture.  On  turning  on  the  current 
the  cork  will  be  driven  up  to  the  ceiling. 

In  the  same  way  India  rubber  balloons  may  be  ex- 
ploded. They  must  be  partially  inflated  with  oxy- 
gen evolved  under  pressure,  and  then  about  twice  the 
volume  of  hydrogen  is  introduced  directly  from  the 


FIG.  45.    FIBE  CRACKER  EXPLOSIONS. 

generating  flask.     A  very  small  cork  is  arranged  with 
the  exploding  wire  connection.     As  the  balloon  is 
filled  its  neck  is  pinched  with  the  finger  well  up  from 
the  end,  and  the  cork  is  dexterously  introduced. 
Common  fire  crackers  may  be  used  as  presented  in 


ELECTRIC  GYMNASTICS.  Ill 

the  cut  to  illustrate  electric  fuses.  All  that  is  neces- 
sary is  to  twist  a  fine  wire  around  the  projecting  fuse 
of  the  cracker,  as  shown  in  the  cut  at  a,  or  to  trans- 
fix the  cracker  with  a  piece  of  fine  wire,  as  shown  at 
J.  "When  a  strong  enough  current  is  sent  through 
the  wire  the  explosion  of  the  fire  cracker  will  follow. 
In  "  rain-making  "  experiments,  conducted  in  the 
arid  zone  in  the  western  United  States,  in  the 
season  of  1891,  large  balloons  of  combustible  gas 
and  oxygen  were  exploded  by  electricity  in  the  hope 
of  producing  rain. 

Electric  Gymnastics. 

A  very  clever  idea  has  taken  shape  in  the  produc- 
tion of  gymnastic  apparatus,  which  in  its  use  pro- 
duces and  administers  electric  shocks.  The  type  of 
apparatus  is  of  the  weight-lifting  kind,  in  which 
s'pade  handles  attached  to  ropes  are  pulled  by  the 
gymnast.  The  strings  run  over  pulleys  and  weights 
are  attached  to  their  ends.  By  varying  the  weights 
the  exercise  may  be  made  more  or  less  severe,  and  by 
different  movements  a  great  variety  of  exercise  may 
be  derived  from  the  comparatively  simple  apparatus. 

The  idea  of  applying  electricity  is  to  cause  these 
movements  to  tie  productive  of  shocks.  This  can  be 
effected  in  several  ways.  The  first  way  to  be 
described  is  by  a  magneto-generator. 

The  cords  of  the  apparatus  have  wires  running 
through  them.  The  handles  are  metallic  and  are  in 


112  ELECTRIC  TOY  MAKING. 

electric  or  metallic  communication  with  the  wire. 
The  magneto-generator  has  already  been  described. 
In  the  ordinary  gymnastic  apparatus  the  pulleys 
are  fastened  about  six  feet  from  the  floor.  At  this 
point  the  generator  is  to  be  secured.  From  the  pulley 
spindle  a  horizontal  axle  runs  along  parallel  with 
the  wall.  The  generator  is  placed  in  such  a  position 
that  this  axle  comes  in  the  prolongation  of  its  own 
axle  and  three  or  four  inches  out  from  the  wall.  The 
axle  passes  through  two  strong  journal  brackets  or 
pillars.  Two  pulleys  with  deep,  wide  grooves  have 
fastened  to  them  the  handle  cords.  A  third  pulley 
has  the  weight-cord  fastened  to  and  wound  around 
it  a  number  of  times. 

Under  this  arrangement  it  is  clear  that,  when  the 
weight  is  up,  the  handles  will  be  free  to  be  pulled 
out  to  the  full  extent.  If  the  weight  descends  it 
will  unroll  its  own  cord,  and  roll  up  the  other  two. 

In  these  movements,  the  bobbin  of  the  generator 
will  turn  with  greater  or  less  velocity,  according  to 
the  way  in  which  the  apparatus  is  handled.  If  the 
wire  handle-cords  are  connected  to  the  terminals  from 
the  bobbin,  the  one  who  manipulates  the  apparatus 
will  receive  a  series  of  electric  shocks.  This  will  be 
more  violent  as  he  works  the  apparatus  more  ener- 
getically. 

The  connection  is  easily  managed.  Perhaps  the 
simplest  way  is  by  springs,  which  bear  against  insu- 
lated metal-coated  drums  or  collectors. 


ELECTRIC  O  TMNAST1CS.  1 1 3 

For  this  method  two  collars  of  wood,  or  other  insu- 
lating material,  are  fastened  to  the  axle,  one  for  each 
handle- cord.  The  collars  have  a  ring  of  brass  around 
their  peripheries.  Each  wire  from  a  handle-cord  is 
soldered,  or  driven  firmly  under  the  brass  on  one  of 
the  collars. 

Copper  or  brass  springs  are  attached  to  the  base- 
board carrying  the  apparatus,  which  lies  flat  against 
the  wall.  There  is  one  spring  for  each  collar,  and 
each  presses  against  the  metal  coating  of  the  collar. 
These  springs  are  in  electric  communication  with 
the  terminals  of  the  magneto-generator. 

Thus  arranged  the  generator  terminals  are  in  con- 
stant connection  with  the  handles,  and  the  person 
operating  receives  the  desired  electrical  excitement. 
It  is  also  possible  to  dispense  with  the  commutator  of 
the  generator  and  simply  connect  the  terminals  from 
the  rotating  bobbins  directly  to  the  handle-wires. 
This  gives,  however,  rather  a  slow  succession  of 
shocks. 

Another  way  of  arranging  the  system  is  to  use  an 
induction  coil.  Then  the  working  of  the  apparatus 
is  caused  to  make  and  break  the  primary  circuit. 

For  this  end,  the  general  features  of  a  rotating 
axle,  with  handle  cord  and  weight-cord  pulleys,  is 
preserved.  The  same  collars  and  springs  are  em- 
ployed also.  Upon  the  back-board  an  induction  coil 
is  mounted.  Its  secondary  terminals  are  carried  to 


114 


ELECTRIC  TOY  MAKING. 


the  two  springs,  thus  being  in  electric  connection 
with  the  handles. 

The  axle  which  rotates  back  and  forth  carries  an 
insulated  circuit  breaking  wheel  of  the  general  type 
of  the  one  shown  in  the  cut.  As  it  has  to  work  in 


CIRCUIT  BREAKER. 

both  directions  of  rotation,  the  wire  that  strikes  the 
teeth  must  be  so  bent  and  shaped  as  to  work  whichever 
way  the  wheel  may  rotate.  Two  springs  press,  one 
against  the  teeth,  the  other  against  the  face  or  frame 
of  the  wheel,  and  connect  wilh  battery  and  primary. 
A  better  arrangement  is  to  mount  a  regular  smooth 
surfaced  commutator  on  the  axle.  This  may  consist 
of  a  wooden  cylinder,  to  which  are  secured  a  number 


ELECTRIC  GYMNASTICS.  115 

of  slips  of  thin  brass  lying  parallel  with  the  axis. 
These  should  be  so  thin  as  to  lie  flush  with  the  wood, 
or  they  may  be  inlaid,  or  embedded  in  it.  Two 
small  screws  will  fasten  each  piece.  A  ring  of  brass 
goes  around  one  end  of  the  commutator  drum,  being 
in  good  electrical  connection  with  all  the  slips. 

One  spring  is  attached  to  the  base  so  as  to  bear 
against  the  ring.  Another  spring  bears  against  the 
drum  to  one  side  of  the  ring.  From  one  spring  a 
wire  goes  to  one  of  the  primary  terminals  of  the  coil. 
From  the  other  spring  a  wire  runs  to  the  battery, 
and  the  other  battery  wire  runs  to  the  other  primary 
terminal  of  the  coil. 

It  Avill  be  understood,  of  course,  that  the  coil  is 
unprovided  with  an  automatic  circuit  breaker,  and 
that  the  manipulation  of  the  apparatus  by  the  gym- 
nast, makes  and  breaks  the  primary  circuit.  This 
induces  a  current  in  the  secondary,  which,  by  the 
spring  connections,  wires  and  metallic  handles,  finds 
its  way  to  the  hands. 

The  coil  should  be  provided  with  a  movable  core,  or 
brass  shielding  tube,  or  else  some  arrangement  for  rais- 
ing and  lowering  the  battery  plates  should  be  provided 
in  order  to  vary  the  strength  of  the  induced  currents. 

The  magneto-generator  gives  shocks  varying  in  in- 
tensity as  well  as  in  frequency.  The  induction  coil 
gives  shocks  of  uniform  intensity,  varying  in  fre- 
quency. The  objection  to  the  latter  is  that  it  needs  a 
battery. 


llfi  ELECTRIC  TOT  MAKING 

It  is  also  to  be  noted  that  the  magneto-generator 
may  be  made  to  supply  the  proper  current  to  the 
primary  of  an  induction  coil,  and  that  the  collecting 
collars  may  connect  with  the  secondary  of  the  coil. 
In  this  method,  the  characteristic  alternating  current 
of  the  generator  works  the  induction  coil  to  advantage, 
without  any  mechanical  make  and  break  device. 

The  primary  of  the  coil  thus  used  should  have  a 
large  number  of  turns,  from  one-eighth  to  one-fourth 
as  many  as  are  in  the  secondary  wire.  The  bobbins 
of  the  generator  should  be  wound  of  the  same  sized 
wire  as  the  primary  of  the  coil.  No.  24  wire  would 
be  a  good  size  for  both. 

Thi^  disposition  will  increase  the  tension  of  the 
circuit,  and  will  give  more  powerful  effects,  as  the 
apparatus  is  more  rapidly  moved. 

Ano—Kato. 

The  words  ANO,  KA.TO,  are  taken  from  the  Greek, 
and  mean  up,  down,  and  allude  to  the  motions  of  the 
objects  seen  in  the  box.  The  cut  shows  its  general 
features  of  construction.  It  is  a  shallow  box  whose 
bottom  and  interior  sides  are  coated  with  tin-foil.  A 
number  of  objects  are  made  out  of  the  lightest  pith- 

The  latter  may  be  of  the  pith  of  cornstalks,  of 
elder  pith,  or,  what  is  still  better,  of  the  pith  of  the 
dry  stalks  of  the  sunflower.  Little  men  with  jointed 
legs  and  arms,  insects,  jointed  snakes,  etc.,  are  made 
out  of  the  pith,  and  may  be  colored  with  a  little  red 


ANO-KATO. 


117 


and  black  ink.     The  box  is  covered  with  u  piece  of 
glass. 

If  the  glass  is  rubbed  with  a  proper  rubber,  it  be- 
comes electrically  excited,  and  attracts  the  objects  in 
the  box.  As  they  ri^e,  they  touch  the  glass  ;  and  as 


FIG.  47.    ANO-KATO. 

they  lie  against  it,  becoming  charged  with  the  same 
electricity,  are  quickly  repelled.  They  fall  into  the 
box  and  are  discharged  by  coming  against  the  tin- 
foil, which,  for  high  potential  difference,  may  be  con- 
sidered to  be  iu  electrical  communication  with  the 
earth. 

This  operation  goes  on  as  long  as  the  rubbing  is 
kept  up. 

For  the  rubber,  a  pad  of  hair,  or  other  material, 
around  which  a  piece  of  kid  glove  is  tied,  is  employed. 


118 


ELECTRIC  TO  Y  MAKING. 


This  may  be  made  much  more  efficient  by  the  use  of 
some  amalgam  such  as  that  used  on  electric  machines. 

Simple  Experiments  in  Static  Electricity. 
Some  simple  experiments  in  static  electricity  are 
next  illustrated.     The  first  cut  shows  a  modification 


r 


PIG.  48.     GLASS  SHOW-CASE  EXPERIMENT. 

of  Ano-Kato.     It  is  supposed  to  be  especially  adapted 
for  use  on  the  interior  of  a  glass  case. 

A  short  silk  thread,  o,  is  stuck  with  a  little  bit  of 
sealing-wax  to  the  interior  of  a  glass  case,  so  as  to 
hang  down  as  shown  in  the  full  line.  If,  now,  the 
exterior  of  the  glass  is  excited  by  rubbing  with  a  silk 
handkerchief,  or  other  electrically  efficient  rubber, 
such  as  the  pad  just  mentioned,  the  thread  will  be 


EXPERIMENTS  IN  STATIC  ELECTRICITY.  119 

agitated  and  drawn  in  one  or  the  other  direction  aa 
shown  by  the  dotted  lines,  I,  c,  following  sometimes 
the  finger.  It  is  needless  to  remark  that  the  move- 
ments thus  excited,  may,  in  their  way,  be  very  curious 
and  amusing.' 

The  next  cut  gives  a  view  of  India  rubber  balloons, 


Fio.  49.    EXPERIMENT  WITH  BALLOONS. 

electrically  excited.  By  striking  these  with  a  rubber 
of  animal  fibre,  or  tissue,  such  as  a  feather  duster, 
they  will  become  highly  excited,  and  will  tend  to 
separate  from  each  other.  The  balloons  are  the  ordin- 
ary India  rubber  ones  sold  in  the  streets  by  peddlers. 


120  ELECTRIC  TOT  MAKING. 

It  is  said  that  three  of  them  may  be  so  excited  ihat 
one  will  adhere  to  the  ceiling,  and  carry  the  other 
two  as  shown.  The  latter  are  represented  as  repelling 
each  other  under  the  same  excitement. 

But  of  these  simple  experi- 
ments, one  of  the  best  is  shown 
in  the  next  illustration.  A 
bunch  of  fine  India  rubber 
threads  is  required.  These 
may  be  procured  at  a  suspender 
factory,  or  other  place,  where 
India  rubber  interwoven  fabrics 
are  made.  The  threads  may  be 
quite  long — six  or  eight  feet  is 
not  too  much. 

The  bunch  of  threads  is  held 
in  one  hand,  by  the  end,  as 
shown,  if  not  too  long,  or 
otherwise  are  suspended  to  the 

FIG.  50  EXPKBIMENTWITH  ceiling,  and  are  gently  stroked 
RUBBER  THREADS.  down  with  a  feather  duster. 
They  all  become  charged  with  the  same  kind  of  elec- 
tricity, and  hence,  each  thread  repels  its  neighbor, 
and  the  whole  bunch  separates.  The  separation  is 
quite  persistent,  and  may  last  a  long  time. 


CHAPTER  VIII. 
HAND  POWER  DYNAMO. 

A  HAND  power  dynamo  is  necessarily  a  rather  feeble 
machine.  But  the  construction  of  one  is  compara- 
tively easy,  and  will  give  good  practice,  the  benefits 
of  which  will  be  felt  if  a  larger  one  is  ever  attempted. 

For  the  sake  of  simplicity  the  well  known  "H" 
armature  is  adopted  m  the  machine  to  be  described, 
and  the  whole  construction  is  designed  to  embody  a 
very  few  parts. 

In  the  illustration,  the  diagonally  shaded  parts 
show  the  section  of  the  field  magnet,  wound  with  two 
coils  of  wire,  as  shown  by  the  vertical  lines  near  its 
base.  The  general  construction  or  design  is  best 
seen  in  the  cut.  The  following  may  be  taken  as  gen- 
eral dimensions  :  Extreme  length  of  field  magnet,  4£ 
inches  ;  height,  including  feet,  4£  inches ;  width,  2 
inches.  The  elevation  may  be  taken  as  on  a  scale  of 
one-fourth  the  natural  size. 

As  shown  in  the  cut,  an  arm  is  cast  on  the  magnet 
to  hold  the  driving  wheel.  It  is  obvious  that  the  arm 
can  be  dispensed  with  and  a  special  standard  used  for 
this  purpose. 


122  ELECTRIC  TOY  MAKING. 

Holes  are  drilled  in  the  foot-flanges  of  the  field- 
magnet,  and  it  is  screwed  down  to  a  base  board  about 
twelve  inches  long  and  six  inches  wide. 

The  field  proper,  or  area  within  Ihe  pole  pieces, 
the  space  in  which  the  armature  rotates,  must  be  as 
exact  a  circle  as  practicable.  The  iron  should  be  of 


FIG.  51.    HAND  POWER  DYNAMO. 

good  quality  and  as  soft  as  possible.     Good  cast  iron 
will  answer  all  requirements. 

The  interior  surface  of  the  pole  pieces  is  sometimes 


HAND  POWER  DYNAMO.  123 

coated  with  tape,  glued  on.  The  portion  to  be  wound 
with  wire  is  smoothly  coated  in  the  same  way.  All 
is  then  ready  for  the  winding. 

One  and  one-half  pounds  of  No.  21  silk-covered 
wire  is  used  to  wind  the  two  field-magnet  coils.  The 
wire  is  weighed  accurately  and  may  be  divided  into 
two  equal  portions,  each  temporarily  on  its  own  reel. 
Otherwise  it  may  be  wound  directly  on  one  of  the 
cores  from  a  single  reel,  and  the  remainder  weighed 
from  time  to  time  to  ascertain  when  one-half  has 
been  employed.  Then  the  other  half  is  wound  on 
the  other  core. 

In  either  case  the  top  core  is  first  wound  over  the 
top  and  away  from  the  operator,  and  as-  closely  and 
evenly  as  possible.  When  partly  wound,  at  short 
intervals,  the  winding  is  tested  with  a  galvanometer 
and  battery.  One  terminal  of  the  battery  is  con- 
nected through  a  galvanometer  with  the  coil  ter- 
minal. The  other  battery  terminal  is  touched  to  the 
iron  of  the  field-magnet.  If  any  deflection  is  pro- 
duced the  winding-  is  defective  in  insulation,  and  is 
in  electric  contact  with  the  field-magnet.  It  must  be 
unwound  and  the  trouble  found  and  rectified. 

In  winding  the  superimposed  layers,  two  pieces  of 
tape,  about  one  inch  longer  than  the  space  wound,  are 
to  be  laid  on.  After  two  or  three  thicknesses  or  lay- 
ers of  wire  have  been  wound  over  it,  the  ends  are 
turned  in  and  over  to  be  secured  by  the  next 
winding.  This  is  repeated  so  as  to  give  a  good  wind- 


124  ELECTRIC  TOT  MAKING. 

ing  surface  and  especially  to  prevent  the  under  layers 
spreading.  After  a  coil  is  wound  it  should  be  gently 
flattened  down  by  blows  with  a  wooden  stick  or 
mallet. 

The  second  or  lower  coil  is  wound  in  the  opposite 
direction  over  the  top  and  towards  the  operator.  If 
the  wire  with  which  the  winding  is  done  is  in  two 
pieces,  two  of  the  ends,  the  last  of  the  upper  and  first 
of  the  lower  coil  must  be  connected  by  twisting  and 
soldering,  leaving  two  ends  free.  The  latter  go 
through  holes  in  the  base-board  to  two  binding 
screws,  one  of  which  onlv  is  shown  in  the  cut. 

The  armature  is  of  "  H  "  section  and  its  spindle  is 
journaled  in  two  strips,  which  are  screwed  or  bolted 
to  the  sides  of  the  field-magnets.  The  places  of 
attachment  of  one  of  these  strips  are  indicated  in  the 
cut  of  the  dynamo  by  two  white  rectangles  with  a 
bolt  hole  in  the  centre  of  each.  These  strips  must  be 
of  brass  or  some  non-magnetic  material,  and  on  no 
account  of  iron  or  steel. 

The  end  view  of  the  armature,  giving  also  its  cross 
section,  is  shown  in  the  next  cut.  It  may  be  of 
soft  cast  iron.  It  is  far  preferable,  if  possible,  to 
build  it  up  of  washers  of  thin  sheet  iron  annealed  and 
oxidized,  or  with  thin  shellacked  paper  placed  between 
each.  In  such  case  each  piece  must  be  perforated, 
but  with  a  square  or  rectangular  aperture,  and  strung 
upon  a  spindle  which  it  closely  fits.  In  such  case 
special  pieces  must  be  used  at  the  ends  to  secure  the 


HAND  POWER  DYNAMO.  125 

necessary  projections  or  horns  shown  more  clearly  in 
the  next  cut,  which  represents  the  end  view  of  the 
armature. 

The  edges  of  the  armature  are  filed  or  smoothed 
off  if  necessary,  and  it  is  wound  with  one  half-pound 


Fiu.  52.    END  VIKW  OP  ARMATURE. 

of  the  same  wire.  The  surface  to  be  wound  must  be 
covered  with  tape,  glued  on.  The  winding  is  led  or 
made  to  begin  from  the  commutator  end  of  the  arma- 
ture, and  is  interrupted  where  the  spindle  comes  as 
shown  in  the  cut  of  the  dynamo,  Fig.  51. 

The  commutator  shown  on  the  left  of  the  spindle 
is  a  block  of  hard  wood  about  throe-quarters  of  an 
inch  in  diameter,  and  three-eighths  of  an  inch 
deep.  A  tube  of  brass  is  driven  over  it  and  is  screwed 
fast  with  short  screws,  which  must  not  reach 
the  spindle.  The  commutator  is  driven  on  to  the 
shaft.  The  brass  tube,  after  being  screwed  in  place,  is 
cut  with  two  oblique  and  narrow  cuts  completely 
separating  it  into  two  halves.  One  of  these  cuts  is 
shown  on  the  commutator  in  Fig.  53. 


126  ELECTRICAL  TOT  MAKING. 

The  two  terminals  of  the  armature  winding  are 
soldered  each  to  one  of  the  commutator  divisions. 

A  driven  pulley  one  inch  in  diameter  is  fastened 
on  the  proper  end  of  the  armature  spindle. 

All  these  parts  must  be  rigidly  secured  together. 


FIG.  53. — ELEVATION  AND  JOURNALISING  OF  AKMATUKK,  COMMUTATOR 
AND  DRIVING  PULLET. 

The  armature  spindle  is  two  and  one-quarter  inches 
long,  -j^-  inch  diameter,  and  the  ends  are  turned 
down  to  -j^-  inch  for  the  bearings.  It  must  turn 
freely  in  the  space  between  the  pole  pieces  with  a 
clearance  of  about  -fa  inch.  This  will  exact  very 
accurate  centering.  It  is  well  to  turn  a  fine  groove  in 
the  centre  of  the  cylindrical  sectors  of  the  armature 
and  to  wrap  a  few  turns  of  wire  around  the  windings, 


HAND  POWER  DYNAMO.  127 

and  within  the  groove  to  stop  the  windings  from 
displacement  by  centrifugal  force. 

Two  springs  or  "  brushes "  of  spring-tempered 
copper,  about  one-half  an  inch  wide,  are  attached  to 
the  base  board  and  bear  against  the  opposite  sides  of 
the  commutator.  From  each  spring  a  wire  may  be 
carried  to  a  binding-post.  This  gives  a.shunt  wound 
machine.  Or  only  one  of  the  field-magnet  terminals 
may  be  carried  to  a  binding-post,  the  other  connect- 
ing with  one  of  the  commutator  brushes.  The  other 
commutator  brush  connects  with  the  other  binding 
post.  This  is  a  series  wound  machine. 

The  driving  pulley  is  about  ten  inches  in  diameter, 
and  like  the  driven  pulley  is  grooved  to  receive  a 
sewing  machine  belt. 

The  proper  position  of  the  commutator  is  found  by 
trial,  twisting  it  back  and  forth  until  the  best  results 
are  obtained. 

Such  a  dynamo,  if  properly  constructed,  will,  at 
1,600  revolutions,  or  at  two  and  one-half  turns  of  the 
driving-wheel  per  second,  give  about  ten  volts  poten- 
tial difference,  and  over  an  ampere  of  current.  Two 
or  three  cells  of  bichromate  battery  will  operate  it  as 
a  motor,  the  driving  belt  being  removed. 


CHAPTER  IX. 
MISCELLANEOUS  RECEIPTS  AND  FORMULAE. 

Kookogey's'  Battery  Solution. — Potassium  bichro- 
mate, 221  parts;  water,  boiling,  1,134  parts;  while 
boiling,  add  concentrated  sulphuric  acid,  very  care- 
fully and  slowly  1,588  parts;  allow  it  to  cool  and  to 
precipitate,  decant  for  use.  All  parts  arc  by  weight. 

Electropoion  Fluid.-M.ix  one  gallon  sulphuric  acid, 
concentrated,  and  three  gallons  of  water.  In  a  sepa- 
rate vessel  dissolve  six  pounds  of  potassium  bichro- 
mate in  two  gallons  of  boiling  water.  Mix  the  two 
solutions.  Use  only  when  perfectly  cold. 

Solution,  for  Amalgamating  Zinc. — Dissolve  one 
part  of  mercury  in  a  mixture  of  two  parts  nitric  and 
four  parts  hydrochloric  acid.  After  solution,  add 
six  parts  more  of  hydrochloric  acid.  A  few  seconds 
immersion  will  amalgamate  ordinary  zincs,  which 
may  then  be  washed  in  clean  water,  and  well  rubbed. 
Amalgamation  by  rubbing  with  metallic  mercury 
and  dilute  acid  is  generally  simpler. 

High  Potential  Battery.— Positive  Element:  Sodium 
amalgam  in  caustic  soda  solution. 

Negative  Element  :  A  carbon  plate  in  chloride  of 
iodine. 


MISCELLANEOUS.  129 

The  electromotive  force  of  this  battery  is  said  to  be 
about  4  volts.  (See  "Electric  World,"  Vol.  6, 
No.  16). 

Chloride  of  Iron  Battery. — This  battery  corres- 
ponds in  construction  with  the  Bunsen  battery^ 
except  that  ferric  chloride  is  used  as  the  depolarizer 
in  place  of  chromic  acid.  After  it  becomes  polarized, 
by  redaction  of  the  ferric  to  ferrous  chloride,  it  will 
recuperate  on  standing,  as  the  air  oxidiz<  s  the  iron 
salt.  As  this  action  i^  slow,  bromine  was  added  to 
the  depolarizing  mixture.  This  gave  a  disagreeable 
odor.  Another  improvement  was  to  add  potassium 
chlorate  with  a  little  hydrochloric  acid,  which  had 
very  little  odor  and  was  found  to  work  very  well. 
The  List  combination  is  described  by  Thomas  Moore, 
in  the  London  Chemical  News. 

Potassium  Permanganate  Cell. — By  using  a  solu- 
tion of  potassium  permanganate  and  ammonium 
chloride  in  water  as  exciting  fluid,  with  carbon  and 
amalgamated  zincs  ;is  the  dements,  a  good  open  cir- 
cuit battery  is  obtained.  A  warm  and  concentrated 
solution  of  potassium  permanganate  may  be  poured 
into  exhausted  and  drained  porous  cells  of  Leclanche 
batteries  to  regenerate  them. 

Dry  Battery. — A  good  mixture  for  dry  batteries  is 
made  up  of  :  Plaster  of  Paris,  4  parts ;  zinc  oxide, 
1  part;  saturated  solution  of  zinc  chloride,  enough  to 
make  a  thick  paste.  The  Carl  Gassncr,  Jr.,  patent 


130  ELECTRIC  TOT  MAKING. 

specifies  :  Sal  ammoniac,  1  part;  plaster  of  Paris, 
3  parts;  zinc  chloride,  one  part;  water,  two  parts. 
All  parts  are  by  weight.  A  zinc  can  may  be  used  as 
at  once  the  cup  and  positive  element ;  a  rod  of  carbon 
is  the  negative  element. 

Smee's  Battery. — This  battery  consists  of  amalga- 
gamated  zinc  positive  and  platinized  silver  negative 
plates,  in  a  single  vessel  with  a  ten  per  cent,  solution 
of  sulphuric  acid.  To  platinize  the  negative  plate, 
dissolve  a  little  platinum  bichloride  in  water  with  a 
little  hydrochloric  acid,  and  decompose  the  solution 
by  a  battery,  using  a  platinum  plate  as  anode 
and  the  silver  plate  as  cathode.  This  produces  a 
deposit  of  platinum  on  the  silver  which  facilitates 
the  escape  of  hydrogen  gas. 

Platinized  Carbon  for  Smee  Batteries  (WALKER). — 
The  carbon  plates  are  first  purified  by  soaking  them 
for  some  days  in  sulphuric  acid  diluted  with  time  to 
four  times  its  volume  of  water  ;  a  tinned  copper  con- 
ductor is  then  fastened  to  one  by  tinned  copper  rivets. 
The  carbon  is  then  platinized  by  electrolysis,  the  car- 
bon plate  being  used  as  the  cathode,  the  anode  being 
either  a  platinum  or  carbon  plate.  The  solution  used 
is  thus  prepared  :  sulphuric  acid,  diluted  with  ten 
times  its  volume  of  water,  is  taken,  and  crystals  of 
platinum  chloride  are  added  until  the  solution  be- 
comes of  a  beautiful  straw  yellow  color.  After  the 
current  has  passed  for  about  twenty  minutes  the  plate 


MISCELLANEOUS.  131 

is  finished ;  it  may  be  tested  by  using  it  as  a  cathode 
in  the  electrolysis  of  water ;  it  ought  to  allow  the 
hydrogen  to  escape  freely,  without  sticking  to  it  in 
the  form  of  bubbles. 

Porous  Pots. — Minimum  leakage  with  distilled 
water  at  14°C.,  15  per  cent,  in  twenty-four  hours. 

Ebonite. — To  keep  ebonite  in  good  order  it  should 
be  occasionally  washed  with  a  solution  of  ammonia 
in  water. 

Non-  Corrosive  Soldering  Fluid. — Mix  water,  8 
parts;  glycerine,  1  part;  lactic  acid,  1  part.  All  by 
weight. 

Low  Temperature,  Solder. — For  use  when  the  parts 
to  be  soldered  will  not  stand  a  high  temperature. 
Finely  divided  copper  (obtained  by  precipitating  a 
solution  of  copper  sulphate  with  zinc)  is  mixed  with 
concentrated  sulphuric  acid  in  a  porcelain  mortar. 
30  to  36  parts  of  copper  are  taken,  according  to  the 
degree  of  hardness  desired,  and  70  parts  of  mercury 
are  stirred  in.  When  the  amalgam  has  completely 
formed,  it  is  washed  with  hot  water  till  all  traces  of 
acid  are  removed.  It  is  then  allowed  to  cool. 

When  this  composition  is  to  be  used,  it  is  heated 
until  it  is  of  the  consistency  of  wax,  so  that  the  sur- 
faces to  be  joined  may  be  readily  smeared  with  it. 
When  cold,  they  adhere  very  strongly. 

To  purify  Mercury  which  has  been  used  for  amal- 
gamating Zincs. — If  one  of  the  new  low  pressure 


132  ELECTRIC  TOT  MAKING. 

distilling  apparatus  be  not  at  hand,  put  the  mercury 
in  a  deep  vessel,  put  plenty  of  dilute  sulphuric  acid 
over  it,  and  place  a  piece  of  carbon  (a  bit  of  an  electric 
light  carbon  answers  very  well)  into  the  mercury; 
weight  it  or  tie  it  down  so  that  there  is  good  contact 
with  the  mercury  ;  this  arrangement  sets  up  local 
action,  and  dissolves  out  all  metallic  impurities  ;  do 
not  carry  the  action  too  far,  as  you  may  dissolve  some 
of  the  mercury  in  the  form  of  mercury  sulphates. 

Gilt  Plumbago  (TABAUBET). — For  giving  a  con- 
ducting surface  to  electrotype  moulds,  .10  gr.  of  chlo- 
ride of  gold  is  dissolved  in  one  litre  of  sulphuric 
ether,  500  to  600  gr.  of  plumbago  (in  fine  powder) 
is  thrown  in,  the  whole  is  poured  out  into  a  large 
dish,  and  exposed  to  air  and  light.  As  the  ether 
evaporates,  the  plumbago  is  stirred  and  turned  over 
with  a  glass  spatula.  The  drying  is  finished  by  a 
moderate  heat,  and  the  plumbago  put  by  for  use. 

Soldering  Wires  (GULLET). — To  solder  iron  wires 
together,  dissolve  chloride  of  zinc  (or  kill  spirit  of 
salt  with  zinc),  add  a  little  hydrochloric  acid  (spirit 
of  salt)  to  clean  the  wire.  The  rain  soon  washes  off 
the  excess  of  chloride  of  zinc.  To  solder  iron  and 
copper  wires  together  the  excess  of  chloride  must  be 
washed  off,  and  the  joint  covered  with  paint  or  resin, 
or  solder  with  resin. 

For  unanncalcd  wires,  solder  at  as  low  a  tempera- 
ture as  possible. 


MISCELLANEOUS.  133 

The  zinc  solution,  or  spirit  of  salt,  should  never  be 
used  except  for  overhead  out-door  lines.  AH  joints 
in  covered  wire,  whether  run  underground  or  above 
ground,  and  all  joints  within  doors,  either  in  covered 
or  uncovered  wire,  should  be  made  with  resin.  No 
spirit  of  salt,  either  pure  or  killed  with  zinc,  should 
ever  be  allowed  in  an  instrument  maker's  shop  or 
dynamo  factory.  Workmen  will  use  it,  if  not  watched. 
Its  presence  may  often  be  detected  by  holding  an 
open  bottle  of  strong  solution  of  ammonia  (liquor 
p.mmoniae)  under  a  newly  made  joint;  if  it  becomes 
surrounded  with  a  slight  white  cloud  or  mist,  spirit 
of  salt  in  some  form  has  been  used. 

Red  Varnish. — For  wood,  interior  of  electro-mag- 
net coils,  galvanometers,  etc.,  dissolve  sealing-wax  in 
alcohol  at  90°;  apply  it  with  a  pencil  when  cold  in 
four  or  five  coats,  until  the  desired  thickness  is 
attained.  It  is  better  to  use  many  coats  than  to 
make  the  varnish  thick. 

Covering  of  the  External  Wires  of  Large  Electro- 
Magnets. — Large  electro-magnets  are  generally  wound 
with  copper  wire,  covered  with  a  double  layer  of 
cotton.  The  outside  layer  is  hardened  by  painting  it 
with  cold,  thick  gum-lac  varnish.  It  is  gently  roasted 
before  a  charcoal  brazier.  The  layer  thus  formed 
is  extremely  hard.  It  is  filed  smooth,  polished  with 
flax  and  fine  pumice  powder,  and  finally  varnished. 

Cement  for  Induction  Coils. — The  proportions  vary 


134  ELECTRIC  TOT  MAKING. 

very  much  but  generally  approximate  to  the  following 
formula: 

Resin,              ....  2  parts. 

Wax, 1      " 

For  hot  countries  slightly  increase  the  proportion 
of  resin. 

Insulation  of  Wires  for  Telegraphy  and  Telephony 
(C.  WiEDEMANK)-Prepareabath  of  potassium  plum- 
bate  by  dissolving  10  gr.  of  litharge  in  a  litre  of 
water,  to  which  200  gr.  of  caustic  potash  have  been 
added,  and  boil  for  about  half  an  hour  ;  it  is  allowed 
to  settle  and  decanted.  The  bath  is  now  ready  for 
use.  The  wire  to  be  insulated  is  attached  to  the 
positive  pole  of  a  battery  or  electroplating  dynamo, 
and  a  small  plate  of  platinum  attached  to  the  nega- 
tive pole  is  dipped  into  the  bath.  The  peroxide  of 
lead  is  formed  on  the  wire,  and  passes  successively 
through  all  the  colors  of  the  spectrum.  The  insula- 
tion becomes  perfect  only  when  the  wire  assumes  its 
last  color,  which  is  a  brownish-black. 

This  perfect  insulation  may  be  utilized  for  gal- 
vanometers or  other  apparatus. 

Chatterton's  Compound. — For  cementing  together 
the  layers  of  gutta-percha  in  cable  cores,  an  excellent 
insulator  of  fairly  low  inductive  capacity. 

Stockholm  Tar,  ...  1  part. 

Resin,          .  .  .  .  .     1     " 

Gutta-percha,  .  .  .  .  3     " 


MISCELLANEOUS.  135 

Is  also  used  for  filling  up  the  interstices  of  shore- 
end  cables.  Its  density  is  about  the  same  as  that  of 
gutta-percha,  but  its  inductive  capacity  is  less. 

Joints  of  Gutta-percha  Covered  Wire  (GULLET). — 
Exact  perfect  cleanliness.  Eemove  the  gutta-percha 
for  about  four  centimetres,  clean  the  wire  with  emery 
paper,  twist  the  wires  together  for  about  two  centi- 
metres, cut  the  ends  off  close,  so  as  to  leave  no  point 
sticking  out.  Solder  with  resin  and  good  solder  con- 
taining plenty  of  tin.  The  gutta-percha  is  then  split, 
and  turned  back  for  about  5  centimetres,  the  soldered 
joint  is  covered  with  Chatterton's  compound,  and  the 
gutta-percha  on  each  side  of  it  is  warmed  and  manip- 
ulated until  the  two  sides  join.  The  joint  is  finished 
with  a  hot  soldering  iron,  taking  care  to  smooth  it  off 
well,  without  burning  it ;  it  is  then  covered  with 
another  layer  of  Chatterton's  compound.  A  sheet  of 
gutta-percha  is  then  taken,  warmed  at  a  spirit  lamp, 
and  drawn  out  carefully  so  as  slightly  to  dimmish  its 
thickness.  "Whilst  both  gutta-percha  and  Chatterton's 
compound  are  warm,  the  sheet  is  laid  on  the  joint, 
and  moulded  around  it  with  the  thumb  and  forefinger. 
The  joint  is  then  trimmed  with  scissors  ;  the  edges 
kneaded  in  and  smoothed  down  with  a  hot  iron. 
When  the  joint  is  cold,  another  coating  of  Chatter- 
ton's  compound  is  applied,  and  covered  with  a  longer 
and  broader  piece  of  sheet  gutta-percha.  The  whole 
is  then  covered  with  a  final  coating  of  Chatter- 
ton's  compound,  spread  with  the  iron,  and  polished 


136  ELECTRIC  TOY  MAKING. 

by  hand  when  cold,  taking  care  to  keep  the  hand 
well  moistened.  It  is  indispensable  to  obtain  inti- 
mate and  perfect  union  between  the  new  gutta- 
percha  and  that  which  covers  the  wire.  A  much 
neater  and  cleaner  joint  cnn  be  made  by  introducing 
the  two  wires  into  a  little  sleeve  of  tinned  iron,  fixing 
it  to  the  wires  by  compressing  it  as  a  metal  tag  is  fixed 
lo  a  lace,  and  afterwards  soldering;  no  points  are 
then  left  sticking  out  at  the  ends  of  the  joint. 

Cement  used  by  Gaston  Plante  for  his  Secondary 
Batteries  is  run  hot  on  the  corks  and  connecting 
strips  of  the  secondary  cells  to  prevent  the  acid  from 
creeping. 

Turner's  Cement,  .  .  1,000  parts. 

Tallow,  or  Beeswax,  .  .         100      " 

Powdered  Alabaster,        .  .  250      " 

Lampblack  (to  color  it  black),  .  2.5  " 

Waterproofing  Wooden  Battery  Cells  (SPRAGUE). — 
When  the  boxes  are  quite  dry  and  warm,  they  arc 
smeared  over  inside  with  a  hot  cement,  composed 
of  four  parts  of  resin  and  one  part  of  gutta-percha, 
with  a  little  boiled  oil. 

It  may  be  noted  that  the  addition  of  boiled  oil 
improves  all  substances  used  for  this  purpose  which 
contain  pitch,  marine  glue,  or  other  viscous  solid, 
tending  to  prevent  them  from  flowing. 

Watertight  Decomposition  Cells  for  Elecfrotyping 
(E.  BERTHOUD). — A  wtll  made  vat  of  oak  may  last 


MISCELLANEOUS.  137 

for  twelve  or  fifteen  years,  if  it  be  smeared  inside  with 
the  following  composition  : 

Burgundy  Pitch,  .  .  1.500  parts. 

Old  Gutta-percha  in  small  shreds,  250      " 

Finely  Powdered  Pumice-stone,  750      " 

Melt  the  gutta-percha,  and  mix  it  well  with  the 
pumice-stone.  Then  add  the  Burgundy  pitch. 
When  the  mixture  is  hot,  smear  the  inside  of  the  vat 
with  it.  Lay  it  on  in  several  coats.  Eoughness  and 
cracks  are  smoothed  off  with  a  hot  soldering  iron. 
The  heat  of  the  iron  makes  the  cement  penetrate  into 
the  pores  of  the  wood,  and  increases  its  adhesion. 
The  vat  will  stand  sulphate  of  copper  baths,  but  not 
baths  containing  cyanide. 

Cap  Cement. — For  joining  glass  tubes  to  brass  caps 
and  fittings,  and  for  similar  purposes,  cap  cement 
is  thus  made  :  Five  parts,  by  weight,  of  resin  are 
melted  with  one  part  of  yellow  wax;  one  part  of  finely 
powdered  Venetian  red  is  stirred  into  the  melted 
mass.  To  apply,  both  surfaces  are  warmed  enough 
to  melt  the  cement,  but  not  too  hot. 

Electrical  Cement. — For  similar  purposes  to  those 
to  which"  Cap  Cement"  is  applied,  the  following 
(Singer's  formula)  cement  may  be  used:  Eosin,  five 
parts ;  beeswax  and  red  ochre,  of  each  1  part;  plaster 
of  Paris,  ^  part.  A  cheaper  formula  gives  rosin,  14 
parts;  red  ochre,  2  parts;  plaster  of  Paris,  1  part. 

Com  position  for  Cushions  of  Ano-Kato,  andof  Fric- 
tional  Electric  Machines. — Canton  advises  the  use  of 


1P>8  ELECTRIC  TOT  MAKING. 

an  amalgam  of  zinc  and  tin.  Kienmayer  gives  the 
following  formula  :  equal  parts  of  zinc  and  tin ;  melt, 
and  add  twice  the  weight  of  alloy  of  mercury.  When 
the  rubbed  plate  or  cylinder  is  of  vulcanite,  the  amal- 
gam must  be  softer  than  when  it  is  of  glass.  In 
France  they  gent-rally  use  mosaic  gold  (bisulphide  of 
tin).  The  amalgam  must  be  reduced  to  fine  powder, 
and  applied  by  the  aid  of  a  little  hard  grease. 

Solution  for  Paper  for  Chemical  Telegraphs. — One 
part  saturated  solution  of  ferrocyanide  of  potassium, 
one  part  saturated  solution  of  nitrate  of  ammonium, 
two  parts  water. 


INDEX. 


PAGE 

ALARM  or  safe  protector  .....  69-72 
Amalgamation  of  zincs  in  bat- 

teries .........................     15 

Ano-Kato  ..................  116-118 

Ano-Kato  in  show  case    ..  .118,119 
Armature,   Page's  rotating.  .  .  .56-59 

Armature,  Page's  rotating,  its 

commutator  ................     58 

Armatures,  rolling  ............  28  29 

Artillery,  electric  .........  107-111 

BALLOONS,     experiment     wilh 
rubber  ...................  119,  120 

Bars,  steel,  to  magnetize  ......  23-28 

Batteries  .......................  9-22 

Batteries,  bichromate  .......  11,12 

Batteries,  copper  sulphate  ......  9,  10 

Batteiics,  dip  .................  11,12 

Batteries,  miniature,  from  elec- 
tric light  carbons  ............     13 

Batteries,  primary,  in  general..      9 
Batteries,  sal  ammoniac  ........    13 

Batteries  with  electric  light  car- 
bons ........................  15-20 

Battery  from  a  tomato  can  ____  20,  21 

Battery,  gravity  ...............     10 

Battery,  Lalande—  Chaperon...    21 
Battery,  Leclanche"  .......  _____  10,  11 

Battery,  silver  chloride  ........  13-15 

Buttery  solution,  Trouve's  .....      12 

Battery  troughs  of  wood  .....    22 

Bells,  electric  ..............  65-72 

Bell,  the  tolling  ...............  65-67 

Bell,  the  vibrating  .............  67-69 

Boat.  Magnetic  ................    36 

lar  alar 


Burgla 


larm  ................  69-72 


CARBONS,  applying  parafflne  to.  16 
Carbons,  electric  light  in  bat- 

teries .......................  15-20 

Cells,  materials  for  ...   ........  21  .  22 

Circle,  the  magic  .............  42,  43 

Circuit  breaker,  pendulum.  .  .  83-85 
Circuit  breakers  for  induction 

coils  .......................  97,98 

Coil,  pendulum  motor  .........  46-49 

Coils,  induction  and  spark  ....  89-104 

Coils,  induction,  condensers 

of  .......  .................  99-101 

Coils,  magnetizing,  to  make.  .  .40-42 
Coils,  spark  and  induction..  .  .89-104 


PA6E 

Coil  to  magnetize  with 27 

Condensers  of  induction  coils 

99-101 

Copal  gum  for  coils 42 

Copper  oxide  in  battery 20, 21 

Core  of  coils,  how  made 89,90 

DANCER,  the  electric 73-76 

Dancer,  the  electric,  battery  re- 
quired for 76 

Drum,  the  magic 76-79 

Dynamo,  hand  power 121-127 

ELECTRIC  artillery 107-111 

Electric  bell,  key  for 67 

Electric  bells 65-72 

Elec'ric  dancer 73-76 

Electric  dancer,  battery  required 

for 7fi 

Electric  gymnastics 111-116 

Electric  hammer 79-82 

Electric  insects 82-87 

Electric  insects,  circuit  breaker 

.  for 83-85 

Electric  insects,  mercury  switch 

for 86,87 

Electric  light  carbons  in  batter- 
ies  15-20 

Electric  locomotive 59-64 

Electric  mortar 107-1 1 1 

Electric  motors 46-64 

Electric  Pistol 108-1 10 

Electro-magnet   from   gas-pipe 

Electro-magnet,  Joule's 38, 39 

Electro-magnets 37^45 

Electro-magnet,  solenoid 39, 40 

Electro-magnets,  their  construc- 
tion  37-10 

FIRE  CRACKER  explosions  and 

fuses 110,111 

Fishes,  magnetic 36 

Force,    lines    of,  followed    bv 

polarizf-d  needle 29, 30 

Formulas  and  receipts,  miscel- 
laneous  128 

Foncanlt's  experiment 32-34 

Fuses,  fire  cracker 110,  111 

GENERATOR,  the  magneto.   .104-107 

Gluing  Coils 41.42 

Gymnastics,  electric  111-116 


140 


INDEX. 


PAGE 

HAMMER,  the  electric 79-82 

Hemispheres,  magnetic 43-45 

Hopkin's  electric  insects 82-87 

Hopkin's  magic  drum 76-79 

INCANDESCENT  lamp 87,88 

Induction  coil,  Recordon's.  .102-104 

Induction  coils  91-104 

Induction  coils,  condensers  of 

99-101 

Insects,  electric 82-87 

Insects,  electric,  circuit  breaker 

83-85 

Insects,  eleciric,  mercury  switch 

for 86,87 

Iron  scraps  in  battery 20 

JACK-STRAWS,  magnetic 30,31 

Joule's  electromagnet 38,39 

KEEPERS  of  magnets 27,28 

Key  for  electric  b?ll 67 

LALANDE-Chaperon  battery 21 

Lamp,  incandescent 87,88 

Lamp,  platinum,  self-regulating 

Locomotive,  ihe  electric. . . . . .  .59'-64 

MAGIC  circle 42,43 

Magic  drum 76-79 

Magnetic  fishes,  swan,  boat,  etc.    3fi 

Magnetic  hemispheres 43-45 

Magnetic  jack-straws 30.31 

Magnetic  pendulum 32-34 

Magnetic  swan 36 

Magnetic  top 31,32 

Magnetizing  by  a  dynamo 25 

Magnetizing  by  an  electro  mag- 
net  25.26 

Magnetizing    by    a  permanent 

magnet.... 24.25 

Magnetizing  coils,  to  make. . .  .40-42 
Magnetizing,  Elia's  method ....  27 
Magnetizing.  Jacobin  method  .26. 27 

Magnetizing  steel  bars  23,28 

Magneti/.ing  with  a  coil 27 

Magneto-generator  104-107 

Magnets,  compound 26 

Magnet*,  ill   effects  of  jariing 

and  filing 28 

Magnets,  permanent 23-36 

Magnets,  to  preserve 27,  ?8 

Mahomet's  coffin 29,30 

Mahomet's  coffin  with  solenoid.    40 

Mayer's  floating  needles 34, 35 

Miscellaneous      formulas     and 
receipts 138-138 


PAGE 

Miscellaneous  toys.  ...• 73  88 

Mortar,  electric 107, 108 

Motor,  multipolar 51-56 

Motor,  multipolar,  its  commuta- 
tor .. 53-55 

Motor,  pendulum  coil 46-49 

Motor,  Recordon  magnet 49-5 1 

Mnltipolar  motor 51-56 

Multipolar  motor,  its  commuta- 
tor  53-55 

NEEDLES,  Mayer's  floating 34, 35 

OXIDE  of  copper  in  battery 20,21 

PAGE'S  rotating  armature 56-59 

Page's    rotating  armature,    its 

commutator 58 

Page's  solenoid  magnets 39 

Paraffine.  applying  to  carbons..    16 

Pendulum  circuit  breaker 83-85 

Pendulum  coil  motor  46-49 

Pendulum,  the  magnetic 32-34 

Pistol,  electric  or  voltaic ....  108-1 10 
RECEIPTS  and  formulas,  miscel- 
laneous  128-138 

R  ('cordon's  induction  coil. .  .102-104 

Recordon  magnet  motor 49-M 

Rolling  armatures 28, 29 

Rolling  armatures,  repulsion  of.  29 
Rotating  armature,  Pag*  's.... 56-59 
Rotating  armature,  Page's,  its 

commutator 58 

Rubber  balloon  experiment. 119, 120 
Rubber  thread  experiment.  ...  120 

SAFE  protector ...  09-72 

Show  case.  Ano-Kato 118,119 

Soda,  caustic,  in  battery 20 

Solenoid  electro-magnet 39.  40 

Solenoid  of  electric  hammer..  .81.  82 

Spark  coils 89, 91 

Static  electricity,  simple  experi- 
ments in 1)8-120 

Steel  bars,  to  magnetize 23-28 

S  ivan,  magnetic 36 

Switch,  mercury,  for  electric  in- 
sects  86.87 

TOLLING  bell r.5-07 

Top,  the  magnetic  31-83 

Toys,  miscellaneous 73-88 

Trouve,  battery  solution 12 

VIBRATING  bell 07-69 

Voltaic  pistol 108-110 

Zmc,  amalgamation  of,  in  bat- 
teries..., .     15 


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